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Draft version February 26 2019Typeset using LATEX twocolumn style in AASTeX62
AstroSat-CZTI detection of variable prompt emission polarization in GRB 171010A
Vikas Chanddagger1 Tanmoy ChattopadhyayDagger2 Gor Oganesyanlowast3 4 A R Rao1 Santosh V Vadawale5
Dipankar Bhattacharya6 V B Bhalerao7 and Kuntal Misra8 9
1Tata Institute of Fundamental Research Mumbai India2Pennsylvania State University State College PA USA
3Gran Sasso Science Institute Viale F Crispi 7 I-67100 LAquila Italy4 INFN - Laboratori Nazionali del Gran Sasso I-67100 LAquila Italy
5Physical Research Laboratory Ahmedabad Gujarat India6The Inter-University Centre for Astronomy and Astrophysics Pune India
7Indian Institute of Technology Bombay India8Aryabhatta Research Institute of observational sciecES (ARIES) Manora Peak Nainital India9Department of Physics University of California 1 Shields Ave Davis CA 95616-5270 USA
ABSTRACT
We present spectro-polarimetric analysis of GRB 171010A using data from AstroSat Fermi and
Swift to provide insights into the physical mechanisms of the prompt radiation and the jet geometry
Prompt emission from GRB 171010A was very bright (fluence gt 10minus4 ergs cmminus2) and had a complex
structure composed of the superimposition of several pulses The energy spectra deviate from the
typical Band function to show a low energy peak sim 15 keV mdash which we interpret as a power-law
with two breaks with a synchrotron origin Alternately the prompt spectra can also be interpreted
as Comptonized emission or a blackbody combined with a Band function Time-resolved analysis
confirms the presence of the low energy component while the peak energy is found to be confined in
the range of 100ndash200 keV
Afterglow emission detected by Fermi-LAT is typical of an external shock model and we constrain
the initial Lorentz factor using the peak time of the emission Swift-XRT measurements of the afterglow
show an indication for a jet break allowing us to constrain the jet opening angle to gt 6
Detection of a large number of Compton scattered events by AstroSat-CZTI provides an opportunity
to study hard X-ray polarization of the prompt emission We find that the burst has high time-variable
polarization with the emission have higher polarization at energies above the peak energy
We discuss all observations in the context of GRB models and polarization arising due to due to
physical or geometric effects synchrotron emission from multiple shocks with ordered or randommagnetic fields Poynting flux dominated jet undergoing abrupt magnetic dissipation sub-photospheric
dissipation a jet consisting of fragmented fireballs and the Comptonization model
Keywords gamma-ray burst general ndash gamma-ray burst individual (GRB 171010A) ndash polarization
ndash radiation mechanisms non-thermal
1 INTRODUCTION
The emission mechanisms of gamma ray bursts
(GRBs) and the radiation processes involved in pro-
ducing the complex structure during the prompt phase
have eluded a complete understanding in spite of the fact
daggervikaschandphysicsgmailcom
Daggertxc344psuedu
lowastgoroganesyangssiit
that these energetic cosmological events have been stud-
ied for more than five decades Based on the duration of
the observed prompt emission GRBs are broadly clas-
sified into two families named as long and short GRBs
with a demarcation at 2 s The long GRBs are found to
be associated with with type Ic supernovae pointing at
their massive star origin To extract energy efficiently to
power a GRB such a collapse results in a black hole or
a rapidly spinning and highly magnetized neutron star
(Woosley amp Bloom 2006 Cano et al 2017) The recent
arX
iv1
807
0173
7v2
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tro-
phH
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24
Feb
2019
2 Chand et al
groundbreaking discovery of gravitational waves and its
electromagnetic counterpart object (a short GRB) re-
solved the problem of identifying progenitors of short
GRBs at least for the case of one joint GWGRB de-
tection (Abbott et al 2016) The commonly accepted
scenario for the production of the emerging radiation is
based on the premise of relativistic jets being launched
from the central engine When the jet pierces through
an ambient medium which is either a constant den-
sity interstellar medium (ISM) or a wind-like medium
whose density varies with distance external shocks are
formed and the generated radiation has contributions
from both the forward and the reverse shocks The
resultant emission constitutes the widely observed af-
terglows in GRBs (Rees amp Meszaros 1992 Meszaros amp
Rees 1993 Meszaros amp Rees 1997 Akerlof et al 1999
Meszaros amp Rees 1999) A plateau phase in the X-ray
emission is however thought to be associated with a
long term central engine activity or the stratification
in Lorentz factor of the ejecta could also give extended
energy injection (Dai amp Lu 1998 Zhang et al 2006)
The prompt emission can arise due to various mech-
anisms the leading candidates among them are (i) in-
crease of the jet Lorentz factor with time leading to
the collision of inner layers with the outer ones gener-
ating internal shocks which produce non-thermal syn-
chrotron emission as the electrons gyrate in the existing
magnetic field (Narayan et al 1992 Rees amp Meszaros
1994) A variant of internal shock model is the Internal-
Collision-induced MAgnetic Reconnection and Turbu-
lence (ICMART) model where abrupt dissipaton occurs
through magnetic reconnections in a Poynting flux domi-
nated jet (Zhang amp Yan 2011) (iii) dissipation occurring
within a fuzzy photosphere the photosphere is specially
invoked to explain the quasi-thermal shape of the spec-
trum The process manifests itself in such a way that
it can produce a non-thermal shape of the spectrum as
well (Beloborodov 2017) (iii) gradual magnetic dissipa-
tion that occurs within the photosphere of a Poynting
flux dominated jet (Beniamini amp Giannios 2017) and (iv)
Comptonization of soft corona photons off the electrons
present in the outgoing relativistic ejecta (Titarchuk
et al 2012 Frontera et al 2013) These models are de-
signed to explain the spectral properties of the prompt
emission of GRBs and are successful to a certain extent
Some prominent features like the evolution of the spec-
tral parameters and the presence of correlations among
GRB observables are not well understood and most of
them remain unexplained within the framework of a sin-
gle model
Another crucial information that can be added to the
existing plethora of observations of the prompt emission
like the spectral and timing properties presence of af-
terglows presence of associated supernovae etc is the
polarization of the prompt emission Detection of po-
larization therefore provides an additional tool to test
the theoretical models of the mechanism of GRB prompt
emission This however has remained a scarcely ex-
plored avenue due to the unavailability of dedicated po-
larimeters and reliable polarization measurements The
Cadmium Zinc Telluride Imager (CZTI) on board As-
troSat offers a new opportunity to reliably measure po-
larization of bright GRBs in the hard X-rays (Chat-
topadhyay et al 2014 Vadawale et al 2015 Chattopad-
hyay et al 2017) The polarization expected from dif-
ferent models of prompt emission is not only different
in magnitude but also in the expected pattern of tem-
poral variability depending on the emission mechanism
jet morphology and view geometry (see eg Covino amp
Gotz 2016) A study of the time variability characteris-
tics is very important because bright GRBs whose spec-
tra have been studied in great detail often found to have
spectra deviating significantly from the standard Band
function conventionally used to model the GRB spectra
(Abdo et al 2009 Izzo et al 2012 Ackermann et al
2010 Vianello et al 2017 Wang et al 2017)
GRB 171010A is a bright GRB and it presents an op-
portunity for a multi-pronged approach to understand
the GRB prompt emission It has been observed by
both Fermi and AstroSat-CZTI Afterglows in gamma-
rays (FermiLAT) X-rays (Swift-XRT) and optical have
been detected and an associated supernova SN 2017htp
has been found on the tenth day of the prompt emission
A redshift z = 033 has been measured spectroscopi-
cally by the extended Public ESO Spectroscopic Survey
for Transient Objects (ePESSTO) optical observations
(Kankare et al 2017) We present here a comprehen-
sive analysis of this GRB using the Fermi observation
for spectral properties and attempt to relate the prompt
spectral properties to the detection of variable high po-
larization using AstroSat-CZTI We present a summary
of the observations in Section 2 The Fermi light curves
and spectra are constructed in various energy bands and
time bins respectively and they are presented in Sections
2 3 and 4 The polarization measurements in different
time intervals and energies are presented in Section 6
We discuss our results and derive conclusions in Section
7 The cosmological parameters chosen were Ωλ = 073
Ωm = 027 and H0 = 70 km Mpcminus1 secminus1 (Komatsu
et al 2009)
2 GRB 171010A
GRB 171010A triggered the Fermi-LAT and Fermi-
GBM at 19005058 UT (T0) on 2017 October 10
Variable prompt emission polarization in GRB 171010A 3
(Omodei et al 2017 Poolakkil amp Meegan 2017) The
observed high peak flux generated an autonomous
re-point request (ARR) in the GBM flight software
and the Fermi telescope slewed to the GBM in-flight
location A target of opportunity observation was
carried out by the Niel Gehrels Swift Observatory
(Evans 2017) and the Swift-XRT localized the burst
to RA(J2000) 6658092 and Dec minus 1046325
(DrsquoAi et al 2017) Swift-XRT followed the burst for
sim 2 times 106 s1 The prompt emission was also observed
by Konus-Wind (Frederiks et al 2017) The fluence
observed in the Fermi-GBM 10 - 1000 keV band from
T0 + 512 sec to T0 + 15155 s is (642 plusmn 005) times 10minus4
erg cmminus2 (Poolakkil amp Meegan 2017) Here T0 is the
trigger time in the Fermi-GBM The first photon in
LAT (gt 100 MeV ) with a probability 09 of its associ-
ation with the source is received at sim T0 + 374 s and
has an energy sim 194 MeV and a photon with energy
close to 1 GeV (930 MeV) is detected at sim 404 s The
highest energy photon (sim 19 GeV ) in the Fermi-LAT
is detected at sim 2890 s The rest frame energy of this
photon is sim 25 GeV
3 LIGHT CURVES
We examined the light curves of the GRB as obtained
from all 12 NaI detectors and found that detectors n7
n8 and nb (using the usual naming conventions) have
significant detections (source angles are n7 69 n8
31 and nb 40) We have used data from all three
detectors to examine the broad emission features of the
GRB For wide band temporal and spectral analysis
however we chose n8 and nb which have higher count
rates than the other detectors and the angles made with
the source direction for these two detectors are less than
50 degrees The time scale used throughout this paper
is relative to the Fermi-GBM trigger time ie t = T minusT0 Of the two BGO scintillation detectors the detector
BGO 1 (b1) which is positioned on the same side on
the satellite as the selected NaI detectors is chosen for
further analysis
The light curve is shown in Figure 1 and it shows
two episodes of emission (a) beginning at sim minus5s of the
main burst and lasts up to sim 205 s followed by a quies-
cent state when the emission level meets the background
level and (b) the emission becomes active again after a
short period at sim 246 s and radiation from the burst is
detected till sim 278 s We name these emission phases
as Episode 1 amp 2 In Figure 1 we also show the light
curve in the 100 - 400 keV region (the energy range of
AstroSat-CZTI observations) and we use this light curve
1 httpwwwswiftacukxrt curves00020778
0 50 100 150 200 250 300
104
n7 + n8 + nb8 - 900 keV
0 50 100 150 200 250 300Time since GBM trigger (s)
2000
4000
6000
8000
n7 + n8 + nb100 - 400 keV
Coun
tss
ec
Figure 1 Fermi-GBM light curve of GRB 171010A ob-tained from three NaI detectors n7 n8 and nbUpper Panel Log-scale light curve in the full energy range(8 ndash 900 keV) binned in 1 s intervals The two emissionepisodes used for time-integrated spectral analysis (minus5 s to205 s 246 s to 278 s) are shaded and demarcated with verti-cal dotted lines The red envelope shows the Bayesian blocksrepresentation of the light curveLower panel Linear-scale light curve and Bayesian blocksrepresentation for the 100 ndash 400 keV energy range used intime-resolved spectral analysis
to divide the data for time resolved spectral analysis
The blocks of constant rate (Bayesian blocks) are con-
structed from the light curves and over-plotted on the
count rate light curves to show statistically significant
changes in them (Scargle et al 2013)
The light curves summed over the chosen GBM detec-
tors (n8 and nb) in six different energy ranges are shown
in Figure 2 The GRB has complex structure with mul-
tiple peaks and the high energy emission (above 1 MeV)
is predominant till about 50 s as seen in the light curve
for gt 1 MeV Bayesian blocks are constructed from the
light curves and over-plotted on the count rate
4 SPECTRAL ANALYSIS
The burst is very bright and even with a signal to
noise ratio of 50 we are able to construct more than
150 time bins We created time bins therefore from
the Bayesian blocks constructed from the light curve in
the energy range 100 keV to 400 keV where CZTI is sen-
sitive for polarization measurements These bins (large
number of Bayesian blocks) track significantly varying
features in the lightcurve and will also be sufficient to
give a substantial idea about the energetics of the burst
The spectra are reduced using Fermi Science tools soft-
4 Chand et al
1200
1400
1600 b1 1 - 30 MeV
1000
2000
3000
b1 03 - 1 MeV
500
1000n8 + nb200 - 300 keV
2000
4000n8 + nb100 - 200 keV
250050007500
n8 + nb30 - 100 keV
0 50 100 150 200Time since GBM trigger (s)
250050007500
n8 + nb 8 - 30 keV
Coun
tss
ec
Figure 2 Fermi-GBM light curve of GRB 171010A in six different energy ranges with Bayesian blocks over-plotted in redAt the highest energies (1 ndash 30 MeV top panel) the emission is low after sim 50 s
ware rmfit2 by standard methodology described in the
tutorial3
GRB prompt emission spectra generally show a typi-
cal shape described by the Band function (Band et al
1993) however for a number of bursts additional com-
ponents are observed in the spectra such as quasi-
thermal components modeled by blackbody function
(Ryde 2005 Page et al 2011 Guiriec et al 2011 Basak
amp Rao 2015) or they show additional non-thermal com-
ponents modeled by a power-law or a power-law with an
exponential cut-off (Abdo et al 2009 Ackermann et al
2013) Additionally for a few cases spectra with a top-
hat shape are also observed and modeled by a Band-
function with an exponential roll-off at higher energies
(Wang et al 2017 Vianello et al 2017)
2 Fermi Science Tools rmfit httpsfermigsfcnasagovsscdataanalysisrmfit
3 Fermi tutorial httpsfermigsfcnasagovsscdataanalysisscitoolsrmfit tutorialhtml
The above models are driven by data and phe-
nomenology The physical models devised to explain
the GRB prompt emission radiation have the syn-
chrotron emission or the Compton scattering as the
core processes The synchrotron spectrum for a pow-
erlaw distribution of electrons consists of power-laws
joined at energies which depend upon cooling frequency
(νc) minimum-injection frequency (νm) and absorption
frequency (νa) The Comptonization models include
inverse Compton scattering as a primary mechanism
(Lazzati et al 2000 Titarchuk et al 2012) Comp-
tonization signatures (XSPEC grbcomp model) have
been detected for a set of GRBs observed by Burst
and Transient Source Experiment (BATSE) on board
Compton Gamma Ray Observatory (Frontera et al
2013) The grbcomp model differs from the other Comp-
tonization model the Compton drag model In the
Compton drag model the single inverse Compton scat-
terings of thermal photons shape the spectrum while
in the grbcomp multiple Compton scatterings are as-
sumed Another major difference is that the scattering
Variable prompt emission polarization in GRB 171010A 5
is off the outflow which is sub-relativistic in case of
grbcomp model while relativistic in the Compton drag
model
We apply this prior knowledge of spectral shapes
from the previous observations of GRBs to study
GRB 171010A The spectra are modeled by various
spectroscopic models available in XSPEC (Arnaud
1996) The statistics pgstat is used for optimization
and testing the various models4 We start with the
Band function and use the other models based upon
the residuals of the data and model fit The functional
form of the Band model used to fit the photon spectrum
is given in Equation 1 (Band et al 1993)
NBand(E) =
KB(E100)
αexp (minusE (2 + α) Ep) E lt Eb
KB(αminus β)Ep [100 (2 + α)](αminusβ) exp (β minus α) (E100)β E ge Eb
(1)
Other models include blackbody5 (BB) and a power
law with two breaks (bkn2pow)6 to model the broad
band spectrum
Nbkn2pow(E) =
KEminusα1 E le E1
KE1α2minusα1Eminusα2 E1 le E le E2
KE1α2minusα1E2
α3minusα2Eminusα3 E ge E3
(2)
For the Comptonization model proposed by Titarchuk
et al 2012 XSPEC local model grbcomp is fit to the pho-
ton spectrum7 The pivotal parameters of this model
are temperature of the seed blackbody spectrum (kTs)
the bulk outflow velocity of the thermal electrons (β)
the electron temperature of the sub-relativistic outflow
(kTe) and the energy index of the Greenrsquos function with
which the formerly Comptonized spectrum is convolved
(αb) Using the normalization of the grbcomp model
the apparent blackbody radius can be obtained To
avoid degeneracy in the parameters or the case when
parameters are difficult to constrain we froze some of
the parameters
To fit the spectra with synchroton radiation model we
implemented a table model for XSPEC We assumed a
population of electrons with a power-law energy distri-
bution (as a result of acceleration) dNdγ prop γminusp for
γ gt γm where γm is the minimum Lorentz factor of
electrons The cooling of electrons by synchrotron ra-
diation is considered in slow and fast cooling regimes
4 httpsheasarcgsfcnasagovxanaduxspecmanualnode293html
5 blackbody model httpsheasarcgsfcnasagovxanaduxspecmanualnode136html
6 bkn2pow model httpsheasarcgsfcnasagovxanaduxspecmanualnode141html
7 grbcomp model httpsheasarcnasagovdocsxanaduxspecmodelsgrbcomphtml
depending on ratio between γm and the cooling Lorentz
factor γc (Sari et al 1998) We computed the resulting
photon spectrum of population of electrons assuming
that the average electron distribution at a given time is
dNdγ prop γminus2 for γc lt γ lt γm and dNdγ prop γminuspminus1
for γ gt γm in fast cooling regime while dNdγ prop γminusp
for γm lt γ lt γc and dNdγ prop γminuspminus1 for γ gt γc in
slow cooling regime The synchrotron model is made of
four free parameters the ratio between characteristic
Lorentz factors γmγc the peak energy of Fν spectrum
Ec which is simply the energy which corresponds to the
cooling frequency the power-law index of electrons dis-
tribution p and the normalization We built the table
model for the range of 01 le γmγc le 100 and 2 le p le 5
To fit the time integrated spectrum of Episode 1 we
use the four models described above (i) Band (ii) Band
+ blackbody (BB) (iii) broken power law (bkn2pow)
and (iv) the Comptonization model (grbcomp) The
best fit parameters of the tested models are reported
in Table 1 The νFν plots along with the residuals
are shown in Figure 3 for the four models used The
Band fit shows deviations at lower energies signifying
deviations from the power law that is used to model the
spectra from the low energy threshold of 8 keV to the
peak energy of the Band function (sim150 keV) We have
examined these residuals in detail by progressively rais-
ing the low energy threshold to 40 keV (greater than
the energy in which the deviations are seen) and ex-
6 Chand et al
trapolating the model to the low energies The low en-
ergy features could still be seen The presence of such
an anomaly is found in previous studies (Tierney et al
2013) and we conclude that a separate low energy fea-
ture in the spectra can exist We included a blackbody
(BB) along with the Band model for higher energies but
the residuals still show a systematic hump We also tried
another model for this feature of the spectrum a pow-
erlaw with two breaks (bkn2pow model) The bkn2pow
model is preferable as the pgstat is much less for the
same number of parameters (∆pgstat = 41) The pres-
ence of a narrow residual hump also necessitate the need
of a sharper break than a smooth blackbody curvature
This also hints that the break does not evolve much in
time and thus is not smeared out The Comptonization
model (grbcomp) however gives the best fit for the time
integrated spectrum of Episode 1 All the parameters of
this model other than β fbflag and log(A) were left
free The parameter β was frozen to the value 02 to
ignore terms O(sim β2) and fbflag was set to zero to in-
clude only the first order bulk Comptonization term A
value of 39 for γ shows deviation for the seed photons
from the seed blackbody spectrum However during the
time resolved spectral analysis as reported in the next
subsection we kept it fixed to 3 to consider a blackbody
spectrum for the seed photons
The isotropic energy (Eγiso) is calculated in the cos-
mological frame of the GRB by integrating the observed
energy spectrum over 1 keV(1 + z) to 10MeV(1 + z)
The tested models differ significantly only at low en-
ergies and yield similar Eγiso We have Eγiso =
22 times 1053 erg for the best fit model grbcomp The
Γ0 minus Eγ iso correlation between the initial Lorentz fac-
tor and the isotropic energy can be used to estimate Γ0
of the fireball ejecta (Liang et al 2010) The estimated
Γ0 is 392+38minus34 The errors are propagated from the nor-
malization and slope of the correlation The episode 2
could be spectrally well described by a simple power-law
and the best fit power-law index is 190+007minus006 for pgstat
274 for 229 degrees of freedom
41 Parameters evolution
We performed time resolved analysis to capture the
variations in the spectral properties by dividing the data
into time segments based on the Bayesian blocks made
from the 100 - 400 keV light curve We test the models
that were used for the time-integrated analysis The de-
viation from Band spectrum at low energies observed in
the time-integrated spectrum is also present in the time-
resolved bins thus justifying the need to use more com-
plex models than the simple Band function We how-
ever find that the three additional models (Band+BB
bknpwl and grbcomp) represent the time resolved spec-
tral data equally well The evolution of the model pa-
rameters is shown in Figure 4 In Fermi-GBM energy
range 8-20 keV is divided into 12 energy channels and
thus it provided sufficient data points to constrain the
power-law or BB temperature whenever BB peak or low
energy break falls well within these energy channels In
case of bkn2pow the low energy index is very steep
(sim minus3) when the break energy E1 found to be close
to the lower edge of the detection band For such cases
we froze the index to minus3 to obtain constraints on the
other parameters of the model When we fit with the
Band function the peak energy Ep shows three pulse
like structures in their temporal evolution and these can
be identified as showing a hard to soft (HTS) evolution
for peaks in the photon flux The first structure in Ep(at sim10 s) can be associated with the enhancement seen
in the gt1 MeV flux (Figure 2 top panel) When the low
energy feature is modeled using bkn2pow almost all the
peak energies fall below 200 keV The variation in the
low energy break (E1) remains concentrated in a very
narrow band (10 minus 20 keV) The best fit parameters
for all the models are presented in Table 5
The evolution of the derived parameters of grbcomp
model such as photospheric radius (Rph) and bulk pa-
rameter (δ) is shown in Figure 6
411 Distribution of parameters
Despite the fact that the best fit to the time integrated
spectrum is the Comptonization model (grbcomp) we
have tested the models (i) Band (ii) bkn2pow (iii)
BB+Band and (iv) grbcomp for the time resolved spec-
tra The distribution of the parameters is presented in
Figure 7 and are summarized here
For the Band function the low energy index α is dis-
tributed with a mean value minus1 (σ = 013) The maxi-
mum value observed is minus025 for a few time bins and in
the other cases α remains mostly belowminus08 The values
of low energy index agree with what is typically observed
for long GRBs (lt α gt= minus1) which is however known
to be harder than the synchrotron radiation in the fast
cooling regime The high energy index follows a bimodal
distribution with a mean value of minus27 (σ = 03) for the
major chunk concentrated around minus3 lt β lt minus2 and can
be interpreted as values normally observed for GRBs
The peak energy Ep is between 32 keV and 365 keV
with a median sim 140 (σ = 83) keV Its distribution also
shows a bimodal nature which reflects the evolution of
Ep
In the case of bkn2pow we observed that when the
lower break energy E1 is near the lower edge of the
detection band the power-law index below E1 is very
Variable prompt emission polarization in GRB 171010A 7
Table 1 The best fit parameters for the time integrated spectrum of GRB 171010A Episode 1
Model
Band α β Ep (keV) pgstatdof
minus115+001minus001 minus240+003
minus003 163+3minus3 2786335
BB+Band α β Ep (keV) kTBB (keV) pgstatdof
minus075+004minus003 minus240+004
minus003 1500+25minus26 58+01
minus01 1465333
bkn2pow α1 α2 α3 E1 (keV) E2 (keV) pgstatdof
048+006minus007 1464+0006
minus0005 233+002minus002 172+04
minus04 1327+23minus23 1421333
grbcomp kTs (keV) kTe (keV) τ αb Rph (1010 cm) pgstatdof
48+05minus04 55+3
minus3 415+018minus015 152+004
minus004 80+22minus20 1281332
Synchrotron model γmγc Ec (keV) p pgstatdof
406+003minus008 216+02
minus04 gt 482 2520335
steep This is expected because there are only a few
channels here and the fit probably gives an unphysical
result We thus fixed the values to minus3 as they are diffi-
cult to constrain by the fits and also hamper the over-
all fitting process Note that bkn2pow model is defined
with an a-priori negative sign with it and we have to
be cautious while comparing it with the Band function
where the indices are defined without a negative sign
For the purpose of comparison we will explicitly reverse
the signs of the bkn2pow indices The mean value of minusα1
is sim 03(σ = 065) Here we have ignored values gt 15
as they form another part of the bimodal distribution
with low E1 during the time when E1 is near the lower
edge of the GBM energy band The mean value of minusα2
is sim minus14 (σ = 022) This forms the second power law
from E1 to E2 The third segment of the emission has
power law index minusα3 with a mean of sim minus26 (σ = 023)
The low energy break E1 has a mean sim 16 (σ = 23) keV
and it falls in a narrow range of 11 to 20 keV The mean
E2 is sim 140 (σ = 32) keV comparable to the mean of
Band function peak energy with a uni-modal distribu-
tion The E2 values are concentrated in the range 93 to
350 keV
When a blackbody is added the fits have an improved
statistics compared to the Band function throughout
the burst (see Figure 5) The blackbody temperature
vary between 4 minus 10 keV with a median of sim 63(σ =
112) keV The α distribution has harder values while
Ep and β are similar to the distributions of their counter-
parts in the Band function The presence of blackbody
does not seem to move the peak energies significantly
albeit an upward shift is noticeable In the grbcomp
model the average temperature of the seed photons was
68 (σ = 08) keV The electron temperature kTe was
found to be 55 (σ = 21) keV We derived the photo-
spheric radius from the normalization of the model We
found the photospheric radius sim 1011 cm The grbcomp
model parameters are reasonable and a photospheric ra-
dius of 1011 cm is consistent with its predictions (Fron-
tera et al 2013)
412 Correlations of parameters
We explore two parameter correlations and present
the graphs in Figure 8
(i) kTBB vs Ep Thermal components observed in a
set of bright Fermi single pulse GRBs are correlated to
the peak of non-thermal emission (Burgess et al 2014a)
The exponent of the power-law relation (Ep prop T q) indi-
cates the position of the photosphere if it is in the coast-
ing phase or acceleration phase The jet is dominated by
magnetic fields when q is 2 and baryonic if q is nearly 1
However these results were found on GRBs with single
pulses and for GRBs made up of overlapping pulses such
criteria may not be valid For GRB 171010A a positive
correlation (Ep prop T 22) between Ep and kTBB is found
with a log linear Pearson correlation coefficient of 081
p-value sim 10minus15 The index points out therefore a
magnetically dominated jet with photosphere below the
saturation radius We will discuss this result coupled
with the polarization results in Section 7 The peak en-
ergy from Band function and BB + Band function are
also found to be correlated Ep Band prop E12p BB+Band
(ii) Correlations among grbcomp parameters Corre-
lations between grbcomp model parameters and other
model parameters are reported in Frontera et al (2013)
We found a strong correlation between peak energy of
the Band function and the bulk parameter (δ) with
log linear Pearson coefficient and p-value r(p) of -068
(sim 10minus9) The seed photon temperature kTBB and
photospheric radius Rph are uncorrelated contrary to a
strong anti-correlation reported in Frontera et al 2013
The seed blackbody temperature and the electron tem-
perature are not correlated consistent with the pre-
dictions of grbcomp model The parameter kTe and
peak energy of BB + Band model are correlated with
kTe prop E1p BB+Band
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
2 Chand et al
groundbreaking discovery of gravitational waves and its
electromagnetic counterpart object (a short GRB) re-
solved the problem of identifying progenitors of short
GRBs at least for the case of one joint GWGRB de-
tection (Abbott et al 2016) The commonly accepted
scenario for the production of the emerging radiation is
based on the premise of relativistic jets being launched
from the central engine When the jet pierces through
an ambient medium which is either a constant den-
sity interstellar medium (ISM) or a wind-like medium
whose density varies with distance external shocks are
formed and the generated radiation has contributions
from both the forward and the reverse shocks The
resultant emission constitutes the widely observed af-
terglows in GRBs (Rees amp Meszaros 1992 Meszaros amp
Rees 1993 Meszaros amp Rees 1997 Akerlof et al 1999
Meszaros amp Rees 1999) A plateau phase in the X-ray
emission is however thought to be associated with a
long term central engine activity or the stratification
in Lorentz factor of the ejecta could also give extended
energy injection (Dai amp Lu 1998 Zhang et al 2006)
The prompt emission can arise due to various mech-
anisms the leading candidates among them are (i) in-
crease of the jet Lorentz factor with time leading to
the collision of inner layers with the outer ones gener-
ating internal shocks which produce non-thermal syn-
chrotron emission as the electrons gyrate in the existing
magnetic field (Narayan et al 1992 Rees amp Meszaros
1994) A variant of internal shock model is the Internal-
Collision-induced MAgnetic Reconnection and Turbu-
lence (ICMART) model where abrupt dissipaton occurs
through magnetic reconnections in a Poynting flux domi-
nated jet (Zhang amp Yan 2011) (iii) dissipation occurring
within a fuzzy photosphere the photosphere is specially
invoked to explain the quasi-thermal shape of the spec-
trum The process manifests itself in such a way that
it can produce a non-thermal shape of the spectrum as
well (Beloborodov 2017) (iii) gradual magnetic dissipa-
tion that occurs within the photosphere of a Poynting
flux dominated jet (Beniamini amp Giannios 2017) and (iv)
Comptonization of soft corona photons off the electrons
present in the outgoing relativistic ejecta (Titarchuk
et al 2012 Frontera et al 2013) These models are de-
signed to explain the spectral properties of the prompt
emission of GRBs and are successful to a certain extent
Some prominent features like the evolution of the spec-
tral parameters and the presence of correlations among
GRB observables are not well understood and most of
them remain unexplained within the framework of a sin-
gle model
Another crucial information that can be added to the
existing plethora of observations of the prompt emission
like the spectral and timing properties presence of af-
terglows presence of associated supernovae etc is the
polarization of the prompt emission Detection of po-
larization therefore provides an additional tool to test
the theoretical models of the mechanism of GRB prompt
emission This however has remained a scarcely ex-
plored avenue due to the unavailability of dedicated po-
larimeters and reliable polarization measurements The
Cadmium Zinc Telluride Imager (CZTI) on board As-
troSat offers a new opportunity to reliably measure po-
larization of bright GRBs in the hard X-rays (Chat-
topadhyay et al 2014 Vadawale et al 2015 Chattopad-
hyay et al 2017) The polarization expected from dif-
ferent models of prompt emission is not only different
in magnitude but also in the expected pattern of tem-
poral variability depending on the emission mechanism
jet morphology and view geometry (see eg Covino amp
Gotz 2016) A study of the time variability characteris-
tics is very important because bright GRBs whose spec-
tra have been studied in great detail often found to have
spectra deviating significantly from the standard Band
function conventionally used to model the GRB spectra
(Abdo et al 2009 Izzo et al 2012 Ackermann et al
2010 Vianello et al 2017 Wang et al 2017)
GRB 171010A is a bright GRB and it presents an op-
portunity for a multi-pronged approach to understand
the GRB prompt emission It has been observed by
both Fermi and AstroSat-CZTI Afterglows in gamma-
rays (FermiLAT) X-rays (Swift-XRT) and optical have
been detected and an associated supernova SN 2017htp
has been found on the tenth day of the prompt emission
A redshift z = 033 has been measured spectroscopi-
cally by the extended Public ESO Spectroscopic Survey
for Transient Objects (ePESSTO) optical observations
(Kankare et al 2017) We present here a comprehen-
sive analysis of this GRB using the Fermi observation
for spectral properties and attempt to relate the prompt
spectral properties to the detection of variable high po-
larization using AstroSat-CZTI We present a summary
of the observations in Section 2 The Fermi light curves
and spectra are constructed in various energy bands and
time bins respectively and they are presented in Sections
2 3 and 4 The polarization measurements in different
time intervals and energies are presented in Section 6
We discuss our results and derive conclusions in Section
7 The cosmological parameters chosen were Ωλ = 073
Ωm = 027 and H0 = 70 km Mpcminus1 secminus1 (Komatsu
et al 2009)
2 GRB 171010A
GRB 171010A triggered the Fermi-LAT and Fermi-
GBM at 19005058 UT (T0) on 2017 October 10
Variable prompt emission polarization in GRB 171010A 3
(Omodei et al 2017 Poolakkil amp Meegan 2017) The
observed high peak flux generated an autonomous
re-point request (ARR) in the GBM flight software
and the Fermi telescope slewed to the GBM in-flight
location A target of opportunity observation was
carried out by the Niel Gehrels Swift Observatory
(Evans 2017) and the Swift-XRT localized the burst
to RA(J2000) 6658092 and Dec minus 1046325
(DrsquoAi et al 2017) Swift-XRT followed the burst for
sim 2 times 106 s1 The prompt emission was also observed
by Konus-Wind (Frederiks et al 2017) The fluence
observed in the Fermi-GBM 10 - 1000 keV band from
T0 + 512 sec to T0 + 15155 s is (642 plusmn 005) times 10minus4
erg cmminus2 (Poolakkil amp Meegan 2017) Here T0 is the
trigger time in the Fermi-GBM The first photon in
LAT (gt 100 MeV ) with a probability 09 of its associ-
ation with the source is received at sim T0 + 374 s and
has an energy sim 194 MeV and a photon with energy
close to 1 GeV (930 MeV) is detected at sim 404 s The
highest energy photon (sim 19 GeV ) in the Fermi-LAT
is detected at sim 2890 s The rest frame energy of this
photon is sim 25 GeV
3 LIGHT CURVES
We examined the light curves of the GRB as obtained
from all 12 NaI detectors and found that detectors n7
n8 and nb (using the usual naming conventions) have
significant detections (source angles are n7 69 n8
31 and nb 40) We have used data from all three
detectors to examine the broad emission features of the
GRB For wide band temporal and spectral analysis
however we chose n8 and nb which have higher count
rates than the other detectors and the angles made with
the source direction for these two detectors are less than
50 degrees The time scale used throughout this paper
is relative to the Fermi-GBM trigger time ie t = T minusT0 Of the two BGO scintillation detectors the detector
BGO 1 (b1) which is positioned on the same side on
the satellite as the selected NaI detectors is chosen for
further analysis
The light curve is shown in Figure 1 and it shows
two episodes of emission (a) beginning at sim minus5s of the
main burst and lasts up to sim 205 s followed by a quies-
cent state when the emission level meets the background
level and (b) the emission becomes active again after a
short period at sim 246 s and radiation from the burst is
detected till sim 278 s We name these emission phases
as Episode 1 amp 2 In Figure 1 we also show the light
curve in the 100 - 400 keV region (the energy range of
AstroSat-CZTI observations) and we use this light curve
1 httpwwwswiftacukxrt curves00020778
0 50 100 150 200 250 300
104
n7 + n8 + nb8 - 900 keV
0 50 100 150 200 250 300Time since GBM trigger (s)
2000
4000
6000
8000
n7 + n8 + nb100 - 400 keV
Coun
tss
ec
Figure 1 Fermi-GBM light curve of GRB 171010A ob-tained from three NaI detectors n7 n8 and nbUpper Panel Log-scale light curve in the full energy range(8 ndash 900 keV) binned in 1 s intervals The two emissionepisodes used for time-integrated spectral analysis (minus5 s to205 s 246 s to 278 s) are shaded and demarcated with verti-cal dotted lines The red envelope shows the Bayesian blocksrepresentation of the light curveLower panel Linear-scale light curve and Bayesian blocksrepresentation for the 100 ndash 400 keV energy range used intime-resolved spectral analysis
to divide the data for time resolved spectral analysis
The blocks of constant rate (Bayesian blocks) are con-
structed from the light curves and over-plotted on the
count rate light curves to show statistically significant
changes in them (Scargle et al 2013)
The light curves summed over the chosen GBM detec-
tors (n8 and nb) in six different energy ranges are shown
in Figure 2 The GRB has complex structure with mul-
tiple peaks and the high energy emission (above 1 MeV)
is predominant till about 50 s as seen in the light curve
for gt 1 MeV Bayesian blocks are constructed from the
light curves and over-plotted on the count rate
4 SPECTRAL ANALYSIS
The burst is very bright and even with a signal to
noise ratio of 50 we are able to construct more than
150 time bins We created time bins therefore from
the Bayesian blocks constructed from the light curve in
the energy range 100 keV to 400 keV where CZTI is sen-
sitive for polarization measurements These bins (large
number of Bayesian blocks) track significantly varying
features in the lightcurve and will also be sufficient to
give a substantial idea about the energetics of the burst
The spectra are reduced using Fermi Science tools soft-
4 Chand et al
1200
1400
1600 b1 1 - 30 MeV
1000
2000
3000
b1 03 - 1 MeV
500
1000n8 + nb200 - 300 keV
2000
4000n8 + nb100 - 200 keV
250050007500
n8 + nb30 - 100 keV
0 50 100 150 200Time since GBM trigger (s)
250050007500
n8 + nb 8 - 30 keV
Coun
tss
ec
Figure 2 Fermi-GBM light curve of GRB 171010A in six different energy ranges with Bayesian blocks over-plotted in redAt the highest energies (1 ndash 30 MeV top panel) the emission is low after sim 50 s
ware rmfit2 by standard methodology described in the
tutorial3
GRB prompt emission spectra generally show a typi-
cal shape described by the Band function (Band et al
1993) however for a number of bursts additional com-
ponents are observed in the spectra such as quasi-
thermal components modeled by blackbody function
(Ryde 2005 Page et al 2011 Guiriec et al 2011 Basak
amp Rao 2015) or they show additional non-thermal com-
ponents modeled by a power-law or a power-law with an
exponential cut-off (Abdo et al 2009 Ackermann et al
2013) Additionally for a few cases spectra with a top-
hat shape are also observed and modeled by a Band-
function with an exponential roll-off at higher energies
(Wang et al 2017 Vianello et al 2017)
2 Fermi Science Tools rmfit httpsfermigsfcnasagovsscdataanalysisrmfit
3 Fermi tutorial httpsfermigsfcnasagovsscdataanalysisscitoolsrmfit tutorialhtml
The above models are driven by data and phe-
nomenology The physical models devised to explain
the GRB prompt emission radiation have the syn-
chrotron emission or the Compton scattering as the
core processes The synchrotron spectrum for a pow-
erlaw distribution of electrons consists of power-laws
joined at energies which depend upon cooling frequency
(νc) minimum-injection frequency (νm) and absorption
frequency (νa) The Comptonization models include
inverse Compton scattering as a primary mechanism
(Lazzati et al 2000 Titarchuk et al 2012) Comp-
tonization signatures (XSPEC grbcomp model) have
been detected for a set of GRBs observed by Burst
and Transient Source Experiment (BATSE) on board
Compton Gamma Ray Observatory (Frontera et al
2013) The grbcomp model differs from the other Comp-
tonization model the Compton drag model In the
Compton drag model the single inverse Compton scat-
terings of thermal photons shape the spectrum while
in the grbcomp multiple Compton scatterings are as-
sumed Another major difference is that the scattering
Variable prompt emission polarization in GRB 171010A 5
is off the outflow which is sub-relativistic in case of
grbcomp model while relativistic in the Compton drag
model
We apply this prior knowledge of spectral shapes
from the previous observations of GRBs to study
GRB 171010A The spectra are modeled by various
spectroscopic models available in XSPEC (Arnaud
1996) The statistics pgstat is used for optimization
and testing the various models4 We start with the
Band function and use the other models based upon
the residuals of the data and model fit The functional
form of the Band model used to fit the photon spectrum
is given in Equation 1 (Band et al 1993)
NBand(E) =
KB(E100)
αexp (minusE (2 + α) Ep) E lt Eb
KB(αminus β)Ep [100 (2 + α)](αminusβ) exp (β minus α) (E100)β E ge Eb
(1)
Other models include blackbody5 (BB) and a power
law with two breaks (bkn2pow)6 to model the broad
band spectrum
Nbkn2pow(E) =
KEminusα1 E le E1
KE1α2minusα1Eminusα2 E1 le E le E2
KE1α2minusα1E2
α3minusα2Eminusα3 E ge E3
(2)
For the Comptonization model proposed by Titarchuk
et al 2012 XSPEC local model grbcomp is fit to the pho-
ton spectrum7 The pivotal parameters of this model
are temperature of the seed blackbody spectrum (kTs)
the bulk outflow velocity of the thermal electrons (β)
the electron temperature of the sub-relativistic outflow
(kTe) and the energy index of the Greenrsquos function with
which the formerly Comptonized spectrum is convolved
(αb) Using the normalization of the grbcomp model
the apparent blackbody radius can be obtained To
avoid degeneracy in the parameters or the case when
parameters are difficult to constrain we froze some of
the parameters
To fit the spectra with synchroton radiation model we
implemented a table model for XSPEC We assumed a
population of electrons with a power-law energy distri-
bution (as a result of acceleration) dNdγ prop γminusp for
γ gt γm where γm is the minimum Lorentz factor of
electrons The cooling of electrons by synchrotron ra-
diation is considered in slow and fast cooling regimes
4 httpsheasarcgsfcnasagovxanaduxspecmanualnode293html
5 blackbody model httpsheasarcgsfcnasagovxanaduxspecmanualnode136html
6 bkn2pow model httpsheasarcgsfcnasagovxanaduxspecmanualnode141html
7 grbcomp model httpsheasarcnasagovdocsxanaduxspecmodelsgrbcomphtml
depending on ratio between γm and the cooling Lorentz
factor γc (Sari et al 1998) We computed the resulting
photon spectrum of population of electrons assuming
that the average electron distribution at a given time is
dNdγ prop γminus2 for γc lt γ lt γm and dNdγ prop γminuspminus1
for γ gt γm in fast cooling regime while dNdγ prop γminusp
for γm lt γ lt γc and dNdγ prop γminuspminus1 for γ gt γc in
slow cooling regime The synchrotron model is made of
four free parameters the ratio between characteristic
Lorentz factors γmγc the peak energy of Fν spectrum
Ec which is simply the energy which corresponds to the
cooling frequency the power-law index of electrons dis-
tribution p and the normalization We built the table
model for the range of 01 le γmγc le 100 and 2 le p le 5
To fit the time integrated spectrum of Episode 1 we
use the four models described above (i) Band (ii) Band
+ blackbody (BB) (iii) broken power law (bkn2pow)
and (iv) the Comptonization model (grbcomp) The
best fit parameters of the tested models are reported
in Table 1 The νFν plots along with the residuals
are shown in Figure 3 for the four models used The
Band fit shows deviations at lower energies signifying
deviations from the power law that is used to model the
spectra from the low energy threshold of 8 keV to the
peak energy of the Band function (sim150 keV) We have
examined these residuals in detail by progressively rais-
ing the low energy threshold to 40 keV (greater than
the energy in which the deviations are seen) and ex-
6 Chand et al
trapolating the model to the low energies The low en-
ergy features could still be seen The presence of such
an anomaly is found in previous studies (Tierney et al
2013) and we conclude that a separate low energy fea-
ture in the spectra can exist We included a blackbody
(BB) along with the Band model for higher energies but
the residuals still show a systematic hump We also tried
another model for this feature of the spectrum a pow-
erlaw with two breaks (bkn2pow model) The bkn2pow
model is preferable as the pgstat is much less for the
same number of parameters (∆pgstat = 41) The pres-
ence of a narrow residual hump also necessitate the need
of a sharper break than a smooth blackbody curvature
This also hints that the break does not evolve much in
time and thus is not smeared out The Comptonization
model (grbcomp) however gives the best fit for the time
integrated spectrum of Episode 1 All the parameters of
this model other than β fbflag and log(A) were left
free The parameter β was frozen to the value 02 to
ignore terms O(sim β2) and fbflag was set to zero to in-
clude only the first order bulk Comptonization term A
value of 39 for γ shows deviation for the seed photons
from the seed blackbody spectrum However during the
time resolved spectral analysis as reported in the next
subsection we kept it fixed to 3 to consider a blackbody
spectrum for the seed photons
The isotropic energy (Eγiso) is calculated in the cos-
mological frame of the GRB by integrating the observed
energy spectrum over 1 keV(1 + z) to 10MeV(1 + z)
The tested models differ significantly only at low en-
ergies and yield similar Eγiso We have Eγiso =
22 times 1053 erg for the best fit model grbcomp The
Γ0 minus Eγ iso correlation between the initial Lorentz fac-
tor and the isotropic energy can be used to estimate Γ0
of the fireball ejecta (Liang et al 2010) The estimated
Γ0 is 392+38minus34 The errors are propagated from the nor-
malization and slope of the correlation The episode 2
could be spectrally well described by a simple power-law
and the best fit power-law index is 190+007minus006 for pgstat
274 for 229 degrees of freedom
41 Parameters evolution
We performed time resolved analysis to capture the
variations in the spectral properties by dividing the data
into time segments based on the Bayesian blocks made
from the 100 - 400 keV light curve We test the models
that were used for the time-integrated analysis The de-
viation from Band spectrum at low energies observed in
the time-integrated spectrum is also present in the time-
resolved bins thus justifying the need to use more com-
plex models than the simple Band function We how-
ever find that the three additional models (Band+BB
bknpwl and grbcomp) represent the time resolved spec-
tral data equally well The evolution of the model pa-
rameters is shown in Figure 4 In Fermi-GBM energy
range 8-20 keV is divided into 12 energy channels and
thus it provided sufficient data points to constrain the
power-law or BB temperature whenever BB peak or low
energy break falls well within these energy channels In
case of bkn2pow the low energy index is very steep
(sim minus3) when the break energy E1 found to be close
to the lower edge of the detection band For such cases
we froze the index to minus3 to obtain constraints on the
other parameters of the model When we fit with the
Band function the peak energy Ep shows three pulse
like structures in their temporal evolution and these can
be identified as showing a hard to soft (HTS) evolution
for peaks in the photon flux The first structure in Ep(at sim10 s) can be associated with the enhancement seen
in the gt1 MeV flux (Figure 2 top panel) When the low
energy feature is modeled using bkn2pow almost all the
peak energies fall below 200 keV The variation in the
low energy break (E1) remains concentrated in a very
narrow band (10 minus 20 keV) The best fit parameters
for all the models are presented in Table 5
The evolution of the derived parameters of grbcomp
model such as photospheric radius (Rph) and bulk pa-
rameter (δ) is shown in Figure 6
411 Distribution of parameters
Despite the fact that the best fit to the time integrated
spectrum is the Comptonization model (grbcomp) we
have tested the models (i) Band (ii) bkn2pow (iii)
BB+Band and (iv) grbcomp for the time resolved spec-
tra The distribution of the parameters is presented in
Figure 7 and are summarized here
For the Band function the low energy index α is dis-
tributed with a mean value minus1 (σ = 013) The maxi-
mum value observed is minus025 for a few time bins and in
the other cases α remains mostly belowminus08 The values
of low energy index agree with what is typically observed
for long GRBs (lt α gt= minus1) which is however known
to be harder than the synchrotron radiation in the fast
cooling regime The high energy index follows a bimodal
distribution with a mean value of minus27 (σ = 03) for the
major chunk concentrated around minus3 lt β lt minus2 and can
be interpreted as values normally observed for GRBs
The peak energy Ep is between 32 keV and 365 keV
with a median sim 140 (σ = 83) keV Its distribution also
shows a bimodal nature which reflects the evolution of
Ep
In the case of bkn2pow we observed that when the
lower break energy E1 is near the lower edge of the
detection band the power-law index below E1 is very
Variable prompt emission polarization in GRB 171010A 7
Table 1 The best fit parameters for the time integrated spectrum of GRB 171010A Episode 1
Model
Band α β Ep (keV) pgstatdof
minus115+001minus001 minus240+003
minus003 163+3minus3 2786335
BB+Band α β Ep (keV) kTBB (keV) pgstatdof
minus075+004minus003 minus240+004
minus003 1500+25minus26 58+01
minus01 1465333
bkn2pow α1 α2 α3 E1 (keV) E2 (keV) pgstatdof
048+006minus007 1464+0006
minus0005 233+002minus002 172+04
minus04 1327+23minus23 1421333
grbcomp kTs (keV) kTe (keV) τ αb Rph (1010 cm) pgstatdof
48+05minus04 55+3
minus3 415+018minus015 152+004
minus004 80+22minus20 1281332
Synchrotron model γmγc Ec (keV) p pgstatdof
406+003minus008 216+02
minus04 gt 482 2520335
steep This is expected because there are only a few
channels here and the fit probably gives an unphysical
result We thus fixed the values to minus3 as they are diffi-
cult to constrain by the fits and also hamper the over-
all fitting process Note that bkn2pow model is defined
with an a-priori negative sign with it and we have to
be cautious while comparing it with the Band function
where the indices are defined without a negative sign
For the purpose of comparison we will explicitly reverse
the signs of the bkn2pow indices The mean value of minusα1
is sim 03(σ = 065) Here we have ignored values gt 15
as they form another part of the bimodal distribution
with low E1 during the time when E1 is near the lower
edge of the GBM energy band The mean value of minusα2
is sim minus14 (σ = 022) This forms the second power law
from E1 to E2 The third segment of the emission has
power law index minusα3 with a mean of sim minus26 (σ = 023)
The low energy break E1 has a mean sim 16 (σ = 23) keV
and it falls in a narrow range of 11 to 20 keV The mean
E2 is sim 140 (σ = 32) keV comparable to the mean of
Band function peak energy with a uni-modal distribu-
tion The E2 values are concentrated in the range 93 to
350 keV
When a blackbody is added the fits have an improved
statistics compared to the Band function throughout
the burst (see Figure 5) The blackbody temperature
vary between 4 minus 10 keV with a median of sim 63(σ =
112) keV The α distribution has harder values while
Ep and β are similar to the distributions of their counter-
parts in the Band function The presence of blackbody
does not seem to move the peak energies significantly
albeit an upward shift is noticeable In the grbcomp
model the average temperature of the seed photons was
68 (σ = 08) keV The electron temperature kTe was
found to be 55 (σ = 21) keV We derived the photo-
spheric radius from the normalization of the model We
found the photospheric radius sim 1011 cm The grbcomp
model parameters are reasonable and a photospheric ra-
dius of 1011 cm is consistent with its predictions (Fron-
tera et al 2013)
412 Correlations of parameters
We explore two parameter correlations and present
the graphs in Figure 8
(i) kTBB vs Ep Thermal components observed in a
set of bright Fermi single pulse GRBs are correlated to
the peak of non-thermal emission (Burgess et al 2014a)
The exponent of the power-law relation (Ep prop T q) indi-
cates the position of the photosphere if it is in the coast-
ing phase or acceleration phase The jet is dominated by
magnetic fields when q is 2 and baryonic if q is nearly 1
However these results were found on GRBs with single
pulses and for GRBs made up of overlapping pulses such
criteria may not be valid For GRB 171010A a positive
correlation (Ep prop T 22) between Ep and kTBB is found
with a log linear Pearson correlation coefficient of 081
p-value sim 10minus15 The index points out therefore a
magnetically dominated jet with photosphere below the
saturation radius We will discuss this result coupled
with the polarization results in Section 7 The peak en-
ergy from Band function and BB + Band function are
also found to be correlated Ep Band prop E12p BB+Band
(ii) Correlations among grbcomp parameters Corre-
lations between grbcomp model parameters and other
model parameters are reported in Frontera et al (2013)
We found a strong correlation between peak energy of
the Band function and the bulk parameter (δ) with
log linear Pearson coefficient and p-value r(p) of -068
(sim 10minus9) The seed photon temperature kTBB and
photospheric radius Rph are uncorrelated contrary to a
strong anti-correlation reported in Frontera et al 2013
The seed blackbody temperature and the electron tem-
perature are not correlated consistent with the pre-
dictions of grbcomp model The parameter kTe and
peak energy of BB + Band model are correlated with
kTe prop E1p BB+Band
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Variable prompt emission polarization in GRB 171010A 3
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to RA(J2000) 6658092 and Dec minus 1046325
(DrsquoAi et al 2017) Swift-XRT followed the burst for
sim 2 times 106 s1 The prompt emission was also observed
by Konus-Wind (Frederiks et al 2017) The fluence
observed in the Fermi-GBM 10 - 1000 keV band from
T0 + 512 sec to T0 + 15155 s is (642 plusmn 005) times 10minus4
erg cmminus2 (Poolakkil amp Meegan 2017) Here T0 is the
trigger time in the Fermi-GBM The first photon in
LAT (gt 100 MeV ) with a probability 09 of its associ-
ation with the source is received at sim T0 + 374 s and
has an energy sim 194 MeV and a photon with energy
close to 1 GeV (930 MeV) is detected at sim 404 s The
highest energy photon (sim 19 GeV ) in the Fermi-LAT
is detected at sim 2890 s The rest frame energy of this
photon is sim 25 GeV
3 LIGHT CURVES
We examined the light curves of the GRB as obtained
from all 12 NaI detectors and found that detectors n7
n8 and nb (using the usual naming conventions) have
significant detections (source angles are n7 69 n8
31 and nb 40) We have used data from all three
detectors to examine the broad emission features of the
GRB For wide band temporal and spectral analysis
however we chose n8 and nb which have higher count
rates than the other detectors and the angles made with
the source direction for these two detectors are less than
50 degrees The time scale used throughout this paper
is relative to the Fermi-GBM trigger time ie t = T minusT0 Of the two BGO scintillation detectors the detector
BGO 1 (b1) which is positioned on the same side on
the satellite as the selected NaI detectors is chosen for
further analysis
The light curve is shown in Figure 1 and it shows
two episodes of emission (a) beginning at sim minus5s of the
main burst and lasts up to sim 205 s followed by a quies-
cent state when the emission level meets the background
level and (b) the emission becomes active again after a
short period at sim 246 s and radiation from the burst is
detected till sim 278 s We name these emission phases
as Episode 1 amp 2 In Figure 1 we also show the light
curve in the 100 - 400 keV region (the energy range of
AstroSat-CZTI observations) and we use this light curve
1 httpwwwswiftacukxrt curves00020778
0 50 100 150 200 250 300
104
n7 + n8 + nb8 - 900 keV
0 50 100 150 200 250 300Time since GBM trigger (s)
2000
4000
6000
8000
n7 + n8 + nb100 - 400 keV
Coun
tss
ec
Figure 1 Fermi-GBM light curve of GRB 171010A ob-tained from three NaI detectors n7 n8 and nbUpper Panel Log-scale light curve in the full energy range(8 ndash 900 keV) binned in 1 s intervals The two emissionepisodes used for time-integrated spectral analysis (minus5 s to205 s 246 s to 278 s) are shaded and demarcated with verti-cal dotted lines The red envelope shows the Bayesian blocksrepresentation of the light curveLower panel Linear-scale light curve and Bayesian blocksrepresentation for the 100 ndash 400 keV energy range used intime-resolved spectral analysis
to divide the data for time resolved spectral analysis
The blocks of constant rate (Bayesian blocks) are con-
structed from the light curves and over-plotted on the
count rate light curves to show statistically significant
changes in them (Scargle et al 2013)
The light curves summed over the chosen GBM detec-
tors (n8 and nb) in six different energy ranges are shown
in Figure 2 The GRB has complex structure with mul-
tiple peaks and the high energy emission (above 1 MeV)
is predominant till about 50 s as seen in the light curve
for gt 1 MeV Bayesian blocks are constructed from the
light curves and over-plotted on the count rate
4 SPECTRAL ANALYSIS
The burst is very bright and even with a signal to
noise ratio of 50 we are able to construct more than
150 time bins We created time bins therefore from
the Bayesian blocks constructed from the light curve in
the energy range 100 keV to 400 keV where CZTI is sen-
sitive for polarization measurements These bins (large
number of Bayesian blocks) track significantly varying
features in the lightcurve and will also be sufficient to
give a substantial idea about the energetics of the burst
The spectra are reduced using Fermi Science tools soft-
4 Chand et al
1200
1400
1600 b1 1 - 30 MeV
1000
2000
3000
b1 03 - 1 MeV
500
1000n8 + nb200 - 300 keV
2000
4000n8 + nb100 - 200 keV
250050007500
n8 + nb30 - 100 keV
0 50 100 150 200Time since GBM trigger (s)
250050007500
n8 + nb 8 - 30 keV
Coun
tss
ec
Figure 2 Fermi-GBM light curve of GRB 171010A in six different energy ranges with Bayesian blocks over-plotted in redAt the highest energies (1 ndash 30 MeV top panel) the emission is low after sim 50 s
ware rmfit2 by standard methodology described in the
tutorial3
GRB prompt emission spectra generally show a typi-
cal shape described by the Band function (Band et al
1993) however for a number of bursts additional com-
ponents are observed in the spectra such as quasi-
thermal components modeled by blackbody function
(Ryde 2005 Page et al 2011 Guiriec et al 2011 Basak
amp Rao 2015) or they show additional non-thermal com-
ponents modeled by a power-law or a power-law with an
exponential cut-off (Abdo et al 2009 Ackermann et al
2013) Additionally for a few cases spectra with a top-
hat shape are also observed and modeled by a Band-
function with an exponential roll-off at higher energies
(Wang et al 2017 Vianello et al 2017)
2 Fermi Science Tools rmfit httpsfermigsfcnasagovsscdataanalysisrmfit
3 Fermi tutorial httpsfermigsfcnasagovsscdataanalysisscitoolsrmfit tutorialhtml
The above models are driven by data and phe-
nomenology The physical models devised to explain
the GRB prompt emission radiation have the syn-
chrotron emission or the Compton scattering as the
core processes The synchrotron spectrum for a pow-
erlaw distribution of electrons consists of power-laws
joined at energies which depend upon cooling frequency
(νc) minimum-injection frequency (νm) and absorption
frequency (νa) The Comptonization models include
inverse Compton scattering as a primary mechanism
(Lazzati et al 2000 Titarchuk et al 2012) Comp-
tonization signatures (XSPEC grbcomp model) have
been detected for a set of GRBs observed by Burst
and Transient Source Experiment (BATSE) on board
Compton Gamma Ray Observatory (Frontera et al
2013) The grbcomp model differs from the other Comp-
tonization model the Compton drag model In the
Compton drag model the single inverse Compton scat-
terings of thermal photons shape the spectrum while
in the grbcomp multiple Compton scatterings are as-
sumed Another major difference is that the scattering
Variable prompt emission polarization in GRB 171010A 5
is off the outflow which is sub-relativistic in case of
grbcomp model while relativistic in the Compton drag
model
We apply this prior knowledge of spectral shapes
from the previous observations of GRBs to study
GRB 171010A The spectra are modeled by various
spectroscopic models available in XSPEC (Arnaud
1996) The statistics pgstat is used for optimization
and testing the various models4 We start with the
Band function and use the other models based upon
the residuals of the data and model fit The functional
form of the Band model used to fit the photon spectrum
is given in Equation 1 (Band et al 1993)
NBand(E) =
KB(E100)
αexp (minusE (2 + α) Ep) E lt Eb
KB(αminus β)Ep [100 (2 + α)](αminusβ) exp (β minus α) (E100)β E ge Eb
(1)
Other models include blackbody5 (BB) and a power
law with two breaks (bkn2pow)6 to model the broad
band spectrum
Nbkn2pow(E) =
KEminusα1 E le E1
KE1α2minusα1Eminusα2 E1 le E le E2
KE1α2minusα1E2
α3minusα2Eminusα3 E ge E3
(2)
For the Comptonization model proposed by Titarchuk
et al 2012 XSPEC local model grbcomp is fit to the pho-
ton spectrum7 The pivotal parameters of this model
are temperature of the seed blackbody spectrum (kTs)
the bulk outflow velocity of the thermal electrons (β)
the electron temperature of the sub-relativistic outflow
(kTe) and the energy index of the Greenrsquos function with
which the formerly Comptonized spectrum is convolved
(αb) Using the normalization of the grbcomp model
the apparent blackbody radius can be obtained To
avoid degeneracy in the parameters or the case when
parameters are difficult to constrain we froze some of
the parameters
To fit the spectra with synchroton radiation model we
implemented a table model for XSPEC We assumed a
population of electrons with a power-law energy distri-
bution (as a result of acceleration) dNdγ prop γminusp for
γ gt γm where γm is the minimum Lorentz factor of
electrons The cooling of electrons by synchrotron ra-
diation is considered in slow and fast cooling regimes
4 httpsheasarcgsfcnasagovxanaduxspecmanualnode293html
5 blackbody model httpsheasarcgsfcnasagovxanaduxspecmanualnode136html
6 bkn2pow model httpsheasarcgsfcnasagovxanaduxspecmanualnode141html
7 grbcomp model httpsheasarcnasagovdocsxanaduxspecmodelsgrbcomphtml
depending on ratio between γm and the cooling Lorentz
factor γc (Sari et al 1998) We computed the resulting
photon spectrum of population of electrons assuming
that the average electron distribution at a given time is
dNdγ prop γminus2 for γc lt γ lt γm and dNdγ prop γminuspminus1
for γ gt γm in fast cooling regime while dNdγ prop γminusp
for γm lt γ lt γc and dNdγ prop γminuspminus1 for γ gt γc in
slow cooling regime The synchrotron model is made of
four free parameters the ratio between characteristic
Lorentz factors γmγc the peak energy of Fν spectrum
Ec which is simply the energy which corresponds to the
cooling frequency the power-law index of electrons dis-
tribution p and the normalization We built the table
model for the range of 01 le γmγc le 100 and 2 le p le 5
To fit the time integrated spectrum of Episode 1 we
use the four models described above (i) Band (ii) Band
+ blackbody (BB) (iii) broken power law (bkn2pow)
and (iv) the Comptonization model (grbcomp) The
best fit parameters of the tested models are reported
in Table 1 The νFν plots along with the residuals
are shown in Figure 3 for the four models used The
Band fit shows deviations at lower energies signifying
deviations from the power law that is used to model the
spectra from the low energy threshold of 8 keV to the
peak energy of the Band function (sim150 keV) We have
examined these residuals in detail by progressively rais-
ing the low energy threshold to 40 keV (greater than
the energy in which the deviations are seen) and ex-
6 Chand et al
trapolating the model to the low energies The low en-
ergy features could still be seen The presence of such
an anomaly is found in previous studies (Tierney et al
2013) and we conclude that a separate low energy fea-
ture in the spectra can exist We included a blackbody
(BB) along with the Band model for higher energies but
the residuals still show a systematic hump We also tried
another model for this feature of the spectrum a pow-
erlaw with two breaks (bkn2pow model) The bkn2pow
model is preferable as the pgstat is much less for the
same number of parameters (∆pgstat = 41) The pres-
ence of a narrow residual hump also necessitate the need
of a sharper break than a smooth blackbody curvature
This also hints that the break does not evolve much in
time and thus is not smeared out The Comptonization
model (grbcomp) however gives the best fit for the time
integrated spectrum of Episode 1 All the parameters of
this model other than β fbflag and log(A) were left
free The parameter β was frozen to the value 02 to
ignore terms O(sim β2) and fbflag was set to zero to in-
clude only the first order bulk Comptonization term A
value of 39 for γ shows deviation for the seed photons
from the seed blackbody spectrum However during the
time resolved spectral analysis as reported in the next
subsection we kept it fixed to 3 to consider a blackbody
spectrum for the seed photons
The isotropic energy (Eγiso) is calculated in the cos-
mological frame of the GRB by integrating the observed
energy spectrum over 1 keV(1 + z) to 10MeV(1 + z)
The tested models differ significantly only at low en-
ergies and yield similar Eγiso We have Eγiso =
22 times 1053 erg for the best fit model grbcomp The
Γ0 minus Eγ iso correlation between the initial Lorentz fac-
tor and the isotropic energy can be used to estimate Γ0
of the fireball ejecta (Liang et al 2010) The estimated
Γ0 is 392+38minus34 The errors are propagated from the nor-
malization and slope of the correlation The episode 2
could be spectrally well described by a simple power-law
and the best fit power-law index is 190+007minus006 for pgstat
274 for 229 degrees of freedom
41 Parameters evolution
We performed time resolved analysis to capture the
variations in the spectral properties by dividing the data
into time segments based on the Bayesian blocks made
from the 100 - 400 keV light curve We test the models
that were used for the time-integrated analysis The de-
viation from Band spectrum at low energies observed in
the time-integrated spectrum is also present in the time-
resolved bins thus justifying the need to use more com-
plex models than the simple Band function We how-
ever find that the three additional models (Band+BB
bknpwl and grbcomp) represent the time resolved spec-
tral data equally well The evolution of the model pa-
rameters is shown in Figure 4 In Fermi-GBM energy
range 8-20 keV is divided into 12 energy channels and
thus it provided sufficient data points to constrain the
power-law or BB temperature whenever BB peak or low
energy break falls well within these energy channels In
case of bkn2pow the low energy index is very steep
(sim minus3) when the break energy E1 found to be close
to the lower edge of the detection band For such cases
we froze the index to minus3 to obtain constraints on the
other parameters of the model When we fit with the
Band function the peak energy Ep shows three pulse
like structures in their temporal evolution and these can
be identified as showing a hard to soft (HTS) evolution
for peaks in the photon flux The first structure in Ep(at sim10 s) can be associated with the enhancement seen
in the gt1 MeV flux (Figure 2 top panel) When the low
energy feature is modeled using bkn2pow almost all the
peak energies fall below 200 keV The variation in the
low energy break (E1) remains concentrated in a very
narrow band (10 minus 20 keV) The best fit parameters
for all the models are presented in Table 5
The evolution of the derived parameters of grbcomp
model such as photospheric radius (Rph) and bulk pa-
rameter (δ) is shown in Figure 6
411 Distribution of parameters
Despite the fact that the best fit to the time integrated
spectrum is the Comptonization model (grbcomp) we
have tested the models (i) Band (ii) bkn2pow (iii)
BB+Band and (iv) grbcomp for the time resolved spec-
tra The distribution of the parameters is presented in
Figure 7 and are summarized here
For the Band function the low energy index α is dis-
tributed with a mean value minus1 (σ = 013) The maxi-
mum value observed is minus025 for a few time bins and in
the other cases α remains mostly belowminus08 The values
of low energy index agree with what is typically observed
for long GRBs (lt α gt= minus1) which is however known
to be harder than the synchrotron radiation in the fast
cooling regime The high energy index follows a bimodal
distribution with a mean value of minus27 (σ = 03) for the
major chunk concentrated around minus3 lt β lt minus2 and can
be interpreted as values normally observed for GRBs
The peak energy Ep is between 32 keV and 365 keV
with a median sim 140 (σ = 83) keV Its distribution also
shows a bimodal nature which reflects the evolution of
Ep
In the case of bkn2pow we observed that when the
lower break energy E1 is near the lower edge of the
detection band the power-law index below E1 is very
Variable prompt emission polarization in GRB 171010A 7
Table 1 The best fit parameters for the time integrated spectrum of GRB 171010A Episode 1
Model
Band α β Ep (keV) pgstatdof
minus115+001minus001 minus240+003
minus003 163+3minus3 2786335
BB+Band α β Ep (keV) kTBB (keV) pgstatdof
minus075+004minus003 minus240+004
minus003 1500+25minus26 58+01
minus01 1465333
bkn2pow α1 α2 α3 E1 (keV) E2 (keV) pgstatdof
048+006minus007 1464+0006
minus0005 233+002minus002 172+04
minus04 1327+23minus23 1421333
grbcomp kTs (keV) kTe (keV) τ αb Rph (1010 cm) pgstatdof
48+05minus04 55+3
minus3 415+018minus015 152+004
minus004 80+22minus20 1281332
Synchrotron model γmγc Ec (keV) p pgstatdof
406+003minus008 216+02
minus04 gt 482 2520335
steep This is expected because there are only a few
channels here and the fit probably gives an unphysical
result We thus fixed the values to minus3 as they are diffi-
cult to constrain by the fits and also hamper the over-
all fitting process Note that bkn2pow model is defined
with an a-priori negative sign with it and we have to
be cautious while comparing it with the Band function
where the indices are defined without a negative sign
For the purpose of comparison we will explicitly reverse
the signs of the bkn2pow indices The mean value of minusα1
is sim 03(σ = 065) Here we have ignored values gt 15
as they form another part of the bimodal distribution
with low E1 during the time when E1 is near the lower
edge of the GBM energy band The mean value of minusα2
is sim minus14 (σ = 022) This forms the second power law
from E1 to E2 The third segment of the emission has
power law index minusα3 with a mean of sim minus26 (σ = 023)
The low energy break E1 has a mean sim 16 (σ = 23) keV
and it falls in a narrow range of 11 to 20 keV The mean
E2 is sim 140 (σ = 32) keV comparable to the mean of
Band function peak energy with a uni-modal distribu-
tion The E2 values are concentrated in the range 93 to
350 keV
When a blackbody is added the fits have an improved
statistics compared to the Band function throughout
the burst (see Figure 5) The blackbody temperature
vary between 4 minus 10 keV with a median of sim 63(σ =
112) keV The α distribution has harder values while
Ep and β are similar to the distributions of their counter-
parts in the Band function The presence of blackbody
does not seem to move the peak energies significantly
albeit an upward shift is noticeable In the grbcomp
model the average temperature of the seed photons was
68 (σ = 08) keV The electron temperature kTe was
found to be 55 (σ = 21) keV We derived the photo-
spheric radius from the normalization of the model We
found the photospheric radius sim 1011 cm The grbcomp
model parameters are reasonable and a photospheric ra-
dius of 1011 cm is consistent with its predictions (Fron-
tera et al 2013)
412 Correlations of parameters
We explore two parameter correlations and present
the graphs in Figure 8
(i) kTBB vs Ep Thermal components observed in a
set of bright Fermi single pulse GRBs are correlated to
the peak of non-thermal emission (Burgess et al 2014a)
The exponent of the power-law relation (Ep prop T q) indi-
cates the position of the photosphere if it is in the coast-
ing phase or acceleration phase The jet is dominated by
magnetic fields when q is 2 and baryonic if q is nearly 1
However these results were found on GRBs with single
pulses and for GRBs made up of overlapping pulses such
criteria may not be valid For GRB 171010A a positive
correlation (Ep prop T 22) between Ep and kTBB is found
with a log linear Pearson correlation coefficient of 081
p-value sim 10minus15 The index points out therefore a
magnetically dominated jet with photosphere below the
saturation radius We will discuss this result coupled
with the polarization results in Section 7 The peak en-
ergy from Band function and BB + Band function are
also found to be correlated Ep Band prop E12p BB+Band
(ii) Correlations among grbcomp parameters Corre-
lations between grbcomp model parameters and other
model parameters are reported in Frontera et al (2013)
We found a strong correlation between peak energy of
the Band function and the bulk parameter (δ) with
log linear Pearson coefficient and p-value r(p) of -068
(sim 10minus9) The seed photon temperature kTBB and
photospheric radius Rph are uncorrelated contrary to a
strong anti-correlation reported in Frontera et al 2013
The seed blackbody temperature and the electron tem-
perature are not correlated consistent with the pre-
dictions of grbcomp model The parameter kTe and
peak energy of BB + Band model are correlated with
kTe prop E1p BB+Band
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Lundman C Vurm I amp Beloborodov A M 2016 ArXiv
e-prints arXiv161101451
Meszaros P amp Rees M J 1993 ApJ 405 278
Meszaros P amp Rees M J 1997 ApJ 476 232
Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
mdash 1999 MNRAS 306 L39
Molinari E Vergani S D Malesani D et al 2007
AampA 469 L13
Narayan R Paczynski B amp Piran T 1992 ApJL 395
L83
Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
642 389
Oganesyan G Nava L Ghirlanda G amp Celotti A
2017 ApJ 846 137
mdash 2018 AampA 616 A138
Omodei N Vianello G amp Ahlgren B 2017 GRB
Coordinates Network Circular Service No 21985
1-2018 (2017) 21985
Page K L Starling R L C Fitzpatrick G et al 2011
MNRAS 416 2078
Poolakkil S amp Meegan C 2017 GRB Coordinates
Network Circular Service No 21992 1-2018 (2017)
21992
Ravasio M E Oganesyan G Ghirlanda G et al 2018
AampA 613 A16
Rees M J amp Meszaros P 1992 MNRAS 258 41P
mdash 1994 ApJL 430 L93
Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
4 Chand et al
1200
1400
1600 b1 1 - 30 MeV
1000
2000
3000
b1 03 - 1 MeV
500
1000n8 + nb200 - 300 keV
2000
4000n8 + nb100 - 200 keV
250050007500
n8 + nb30 - 100 keV
0 50 100 150 200Time since GBM trigger (s)
250050007500
n8 + nb 8 - 30 keV
Coun
tss
ec
Figure 2 Fermi-GBM light curve of GRB 171010A in six different energy ranges with Bayesian blocks over-plotted in redAt the highest energies (1 ndash 30 MeV top panel) the emission is low after sim 50 s
ware rmfit2 by standard methodology described in the
tutorial3
GRB prompt emission spectra generally show a typi-
cal shape described by the Band function (Band et al
1993) however for a number of bursts additional com-
ponents are observed in the spectra such as quasi-
thermal components modeled by blackbody function
(Ryde 2005 Page et al 2011 Guiriec et al 2011 Basak
amp Rao 2015) or they show additional non-thermal com-
ponents modeled by a power-law or a power-law with an
exponential cut-off (Abdo et al 2009 Ackermann et al
2013) Additionally for a few cases spectra with a top-
hat shape are also observed and modeled by a Band-
function with an exponential roll-off at higher energies
(Wang et al 2017 Vianello et al 2017)
2 Fermi Science Tools rmfit httpsfermigsfcnasagovsscdataanalysisrmfit
3 Fermi tutorial httpsfermigsfcnasagovsscdataanalysisscitoolsrmfit tutorialhtml
The above models are driven by data and phe-
nomenology The physical models devised to explain
the GRB prompt emission radiation have the syn-
chrotron emission or the Compton scattering as the
core processes The synchrotron spectrum for a pow-
erlaw distribution of electrons consists of power-laws
joined at energies which depend upon cooling frequency
(νc) minimum-injection frequency (νm) and absorption
frequency (νa) The Comptonization models include
inverse Compton scattering as a primary mechanism
(Lazzati et al 2000 Titarchuk et al 2012) Comp-
tonization signatures (XSPEC grbcomp model) have
been detected for a set of GRBs observed by Burst
and Transient Source Experiment (BATSE) on board
Compton Gamma Ray Observatory (Frontera et al
2013) The grbcomp model differs from the other Comp-
tonization model the Compton drag model In the
Compton drag model the single inverse Compton scat-
terings of thermal photons shape the spectrum while
in the grbcomp multiple Compton scatterings are as-
sumed Another major difference is that the scattering
Variable prompt emission polarization in GRB 171010A 5
is off the outflow which is sub-relativistic in case of
grbcomp model while relativistic in the Compton drag
model
We apply this prior knowledge of spectral shapes
from the previous observations of GRBs to study
GRB 171010A The spectra are modeled by various
spectroscopic models available in XSPEC (Arnaud
1996) The statistics pgstat is used for optimization
and testing the various models4 We start with the
Band function and use the other models based upon
the residuals of the data and model fit The functional
form of the Band model used to fit the photon spectrum
is given in Equation 1 (Band et al 1993)
NBand(E) =
KB(E100)
αexp (minusE (2 + α) Ep) E lt Eb
KB(αminus β)Ep [100 (2 + α)](αminusβ) exp (β minus α) (E100)β E ge Eb
(1)
Other models include blackbody5 (BB) and a power
law with two breaks (bkn2pow)6 to model the broad
band spectrum
Nbkn2pow(E) =
KEminusα1 E le E1
KE1α2minusα1Eminusα2 E1 le E le E2
KE1α2minusα1E2
α3minusα2Eminusα3 E ge E3
(2)
For the Comptonization model proposed by Titarchuk
et al 2012 XSPEC local model grbcomp is fit to the pho-
ton spectrum7 The pivotal parameters of this model
are temperature of the seed blackbody spectrum (kTs)
the bulk outflow velocity of the thermal electrons (β)
the electron temperature of the sub-relativistic outflow
(kTe) and the energy index of the Greenrsquos function with
which the formerly Comptonized spectrum is convolved
(αb) Using the normalization of the grbcomp model
the apparent blackbody radius can be obtained To
avoid degeneracy in the parameters or the case when
parameters are difficult to constrain we froze some of
the parameters
To fit the spectra with synchroton radiation model we
implemented a table model for XSPEC We assumed a
population of electrons with a power-law energy distri-
bution (as a result of acceleration) dNdγ prop γminusp for
γ gt γm where γm is the minimum Lorentz factor of
electrons The cooling of electrons by synchrotron ra-
diation is considered in slow and fast cooling regimes
4 httpsheasarcgsfcnasagovxanaduxspecmanualnode293html
5 blackbody model httpsheasarcgsfcnasagovxanaduxspecmanualnode136html
6 bkn2pow model httpsheasarcgsfcnasagovxanaduxspecmanualnode141html
7 grbcomp model httpsheasarcnasagovdocsxanaduxspecmodelsgrbcomphtml
depending on ratio between γm and the cooling Lorentz
factor γc (Sari et al 1998) We computed the resulting
photon spectrum of population of electrons assuming
that the average electron distribution at a given time is
dNdγ prop γminus2 for γc lt γ lt γm and dNdγ prop γminuspminus1
for γ gt γm in fast cooling regime while dNdγ prop γminusp
for γm lt γ lt γc and dNdγ prop γminuspminus1 for γ gt γc in
slow cooling regime The synchrotron model is made of
four free parameters the ratio between characteristic
Lorentz factors γmγc the peak energy of Fν spectrum
Ec which is simply the energy which corresponds to the
cooling frequency the power-law index of electrons dis-
tribution p and the normalization We built the table
model for the range of 01 le γmγc le 100 and 2 le p le 5
To fit the time integrated spectrum of Episode 1 we
use the four models described above (i) Band (ii) Band
+ blackbody (BB) (iii) broken power law (bkn2pow)
and (iv) the Comptonization model (grbcomp) The
best fit parameters of the tested models are reported
in Table 1 The νFν plots along with the residuals
are shown in Figure 3 for the four models used The
Band fit shows deviations at lower energies signifying
deviations from the power law that is used to model the
spectra from the low energy threshold of 8 keV to the
peak energy of the Band function (sim150 keV) We have
examined these residuals in detail by progressively rais-
ing the low energy threshold to 40 keV (greater than
the energy in which the deviations are seen) and ex-
6 Chand et al
trapolating the model to the low energies The low en-
ergy features could still be seen The presence of such
an anomaly is found in previous studies (Tierney et al
2013) and we conclude that a separate low energy fea-
ture in the spectra can exist We included a blackbody
(BB) along with the Band model for higher energies but
the residuals still show a systematic hump We also tried
another model for this feature of the spectrum a pow-
erlaw with two breaks (bkn2pow model) The bkn2pow
model is preferable as the pgstat is much less for the
same number of parameters (∆pgstat = 41) The pres-
ence of a narrow residual hump also necessitate the need
of a sharper break than a smooth blackbody curvature
This also hints that the break does not evolve much in
time and thus is not smeared out The Comptonization
model (grbcomp) however gives the best fit for the time
integrated spectrum of Episode 1 All the parameters of
this model other than β fbflag and log(A) were left
free The parameter β was frozen to the value 02 to
ignore terms O(sim β2) and fbflag was set to zero to in-
clude only the first order bulk Comptonization term A
value of 39 for γ shows deviation for the seed photons
from the seed blackbody spectrum However during the
time resolved spectral analysis as reported in the next
subsection we kept it fixed to 3 to consider a blackbody
spectrum for the seed photons
The isotropic energy (Eγiso) is calculated in the cos-
mological frame of the GRB by integrating the observed
energy spectrum over 1 keV(1 + z) to 10MeV(1 + z)
The tested models differ significantly only at low en-
ergies and yield similar Eγiso We have Eγiso =
22 times 1053 erg for the best fit model grbcomp The
Γ0 minus Eγ iso correlation between the initial Lorentz fac-
tor and the isotropic energy can be used to estimate Γ0
of the fireball ejecta (Liang et al 2010) The estimated
Γ0 is 392+38minus34 The errors are propagated from the nor-
malization and slope of the correlation The episode 2
could be spectrally well described by a simple power-law
and the best fit power-law index is 190+007minus006 for pgstat
274 for 229 degrees of freedom
41 Parameters evolution
We performed time resolved analysis to capture the
variations in the spectral properties by dividing the data
into time segments based on the Bayesian blocks made
from the 100 - 400 keV light curve We test the models
that were used for the time-integrated analysis The de-
viation from Band spectrum at low energies observed in
the time-integrated spectrum is also present in the time-
resolved bins thus justifying the need to use more com-
plex models than the simple Band function We how-
ever find that the three additional models (Band+BB
bknpwl and grbcomp) represent the time resolved spec-
tral data equally well The evolution of the model pa-
rameters is shown in Figure 4 In Fermi-GBM energy
range 8-20 keV is divided into 12 energy channels and
thus it provided sufficient data points to constrain the
power-law or BB temperature whenever BB peak or low
energy break falls well within these energy channels In
case of bkn2pow the low energy index is very steep
(sim minus3) when the break energy E1 found to be close
to the lower edge of the detection band For such cases
we froze the index to minus3 to obtain constraints on the
other parameters of the model When we fit with the
Band function the peak energy Ep shows three pulse
like structures in their temporal evolution and these can
be identified as showing a hard to soft (HTS) evolution
for peaks in the photon flux The first structure in Ep(at sim10 s) can be associated with the enhancement seen
in the gt1 MeV flux (Figure 2 top panel) When the low
energy feature is modeled using bkn2pow almost all the
peak energies fall below 200 keV The variation in the
low energy break (E1) remains concentrated in a very
narrow band (10 minus 20 keV) The best fit parameters
for all the models are presented in Table 5
The evolution of the derived parameters of grbcomp
model such as photospheric radius (Rph) and bulk pa-
rameter (δ) is shown in Figure 6
411 Distribution of parameters
Despite the fact that the best fit to the time integrated
spectrum is the Comptonization model (grbcomp) we
have tested the models (i) Band (ii) bkn2pow (iii)
BB+Band and (iv) grbcomp for the time resolved spec-
tra The distribution of the parameters is presented in
Figure 7 and are summarized here
For the Band function the low energy index α is dis-
tributed with a mean value minus1 (σ = 013) The maxi-
mum value observed is minus025 for a few time bins and in
the other cases α remains mostly belowminus08 The values
of low energy index agree with what is typically observed
for long GRBs (lt α gt= minus1) which is however known
to be harder than the synchrotron radiation in the fast
cooling regime The high energy index follows a bimodal
distribution with a mean value of minus27 (σ = 03) for the
major chunk concentrated around minus3 lt β lt minus2 and can
be interpreted as values normally observed for GRBs
The peak energy Ep is between 32 keV and 365 keV
with a median sim 140 (σ = 83) keV Its distribution also
shows a bimodal nature which reflects the evolution of
Ep
In the case of bkn2pow we observed that when the
lower break energy E1 is near the lower edge of the
detection band the power-law index below E1 is very
Variable prompt emission polarization in GRB 171010A 7
Table 1 The best fit parameters for the time integrated spectrum of GRB 171010A Episode 1
Model
Band α β Ep (keV) pgstatdof
minus115+001minus001 minus240+003
minus003 163+3minus3 2786335
BB+Band α β Ep (keV) kTBB (keV) pgstatdof
minus075+004minus003 minus240+004
minus003 1500+25minus26 58+01
minus01 1465333
bkn2pow α1 α2 α3 E1 (keV) E2 (keV) pgstatdof
048+006minus007 1464+0006
minus0005 233+002minus002 172+04
minus04 1327+23minus23 1421333
grbcomp kTs (keV) kTe (keV) τ αb Rph (1010 cm) pgstatdof
48+05minus04 55+3
minus3 415+018minus015 152+004
minus004 80+22minus20 1281332
Synchrotron model γmγc Ec (keV) p pgstatdof
406+003minus008 216+02
minus04 gt 482 2520335
steep This is expected because there are only a few
channels here and the fit probably gives an unphysical
result We thus fixed the values to minus3 as they are diffi-
cult to constrain by the fits and also hamper the over-
all fitting process Note that bkn2pow model is defined
with an a-priori negative sign with it and we have to
be cautious while comparing it with the Band function
where the indices are defined without a negative sign
For the purpose of comparison we will explicitly reverse
the signs of the bkn2pow indices The mean value of minusα1
is sim 03(σ = 065) Here we have ignored values gt 15
as they form another part of the bimodal distribution
with low E1 during the time when E1 is near the lower
edge of the GBM energy band The mean value of minusα2
is sim minus14 (σ = 022) This forms the second power law
from E1 to E2 The third segment of the emission has
power law index minusα3 with a mean of sim minus26 (σ = 023)
The low energy break E1 has a mean sim 16 (σ = 23) keV
and it falls in a narrow range of 11 to 20 keV The mean
E2 is sim 140 (σ = 32) keV comparable to the mean of
Band function peak energy with a uni-modal distribu-
tion The E2 values are concentrated in the range 93 to
350 keV
When a blackbody is added the fits have an improved
statistics compared to the Band function throughout
the burst (see Figure 5) The blackbody temperature
vary between 4 minus 10 keV with a median of sim 63(σ =
112) keV The α distribution has harder values while
Ep and β are similar to the distributions of their counter-
parts in the Band function The presence of blackbody
does not seem to move the peak energies significantly
albeit an upward shift is noticeable In the grbcomp
model the average temperature of the seed photons was
68 (σ = 08) keV The electron temperature kTe was
found to be 55 (σ = 21) keV We derived the photo-
spheric radius from the normalization of the model We
found the photospheric radius sim 1011 cm The grbcomp
model parameters are reasonable and a photospheric ra-
dius of 1011 cm is consistent with its predictions (Fron-
tera et al 2013)
412 Correlations of parameters
We explore two parameter correlations and present
the graphs in Figure 8
(i) kTBB vs Ep Thermal components observed in a
set of bright Fermi single pulse GRBs are correlated to
the peak of non-thermal emission (Burgess et al 2014a)
The exponent of the power-law relation (Ep prop T q) indi-
cates the position of the photosphere if it is in the coast-
ing phase or acceleration phase The jet is dominated by
magnetic fields when q is 2 and baryonic if q is nearly 1
However these results were found on GRBs with single
pulses and for GRBs made up of overlapping pulses such
criteria may not be valid For GRB 171010A a positive
correlation (Ep prop T 22) between Ep and kTBB is found
with a log linear Pearson correlation coefficient of 081
p-value sim 10minus15 The index points out therefore a
magnetically dominated jet with photosphere below the
saturation radius We will discuss this result coupled
with the polarization results in Section 7 The peak en-
ergy from Band function and BB + Band function are
also found to be correlated Ep Band prop E12p BB+Band
(ii) Correlations among grbcomp parameters Corre-
lations between grbcomp model parameters and other
model parameters are reported in Frontera et al (2013)
We found a strong correlation between peak energy of
the Band function and the bulk parameter (δ) with
log linear Pearson coefficient and p-value r(p) of -068
(sim 10minus9) The seed photon temperature kTBB and
photospheric radius Rph are uncorrelated contrary to a
strong anti-correlation reported in Frontera et al 2013
The seed blackbody temperature and the electron tem-
perature are not correlated consistent with the pre-
dictions of grbcomp model The parameter kTe and
peak energy of BB + Band model are correlated with
kTe prop E1p BB+Band
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Gao H amp Zhang B 2015 ApJ 801 103
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ApJL 727 L33
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Lloyd N M amp Petrosian V 2000 ApJ 543 722
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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Molinari E Vergani S D Malesani D et al 2007
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Narayan R Paczynski B amp Piran T 1992 ApJL 395
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Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
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Oganesyan G Nava L Ghirlanda G amp Celotti A
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Ravasio M E Oganesyan G Ghirlanda G et al 2018
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Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
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Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
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amp Zhang B 2016 ApJ 816 72
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Nature Astronomy 2 69
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751 90
Variable prompt emission polarization in GRB 171010A 5
is off the outflow which is sub-relativistic in case of
grbcomp model while relativistic in the Compton drag
model
We apply this prior knowledge of spectral shapes
from the previous observations of GRBs to study
GRB 171010A The spectra are modeled by various
spectroscopic models available in XSPEC (Arnaud
1996) The statistics pgstat is used for optimization
and testing the various models4 We start with the
Band function and use the other models based upon
the residuals of the data and model fit The functional
form of the Band model used to fit the photon spectrum
is given in Equation 1 (Band et al 1993)
NBand(E) =
KB(E100)
αexp (minusE (2 + α) Ep) E lt Eb
KB(αminus β)Ep [100 (2 + α)](αminusβ) exp (β minus α) (E100)β E ge Eb
(1)
Other models include blackbody5 (BB) and a power
law with two breaks (bkn2pow)6 to model the broad
band spectrum
Nbkn2pow(E) =
KEminusα1 E le E1
KE1α2minusα1Eminusα2 E1 le E le E2
KE1α2minusα1E2
α3minusα2Eminusα3 E ge E3
(2)
For the Comptonization model proposed by Titarchuk
et al 2012 XSPEC local model grbcomp is fit to the pho-
ton spectrum7 The pivotal parameters of this model
are temperature of the seed blackbody spectrum (kTs)
the bulk outflow velocity of the thermal electrons (β)
the electron temperature of the sub-relativistic outflow
(kTe) and the energy index of the Greenrsquos function with
which the formerly Comptonized spectrum is convolved
(αb) Using the normalization of the grbcomp model
the apparent blackbody radius can be obtained To
avoid degeneracy in the parameters or the case when
parameters are difficult to constrain we froze some of
the parameters
To fit the spectra with synchroton radiation model we
implemented a table model for XSPEC We assumed a
population of electrons with a power-law energy distri-
bution (as a result of acceleration) dNdγ prop γminusp for
γ gt γm where γm is the minimum Lorentz factor of
electrons The cooling of electrons by synchrotron ra-
diation is considered in slow and fast cooling regimes
4 httpsheasarcgsfcnasagovxanaduxspecmanualnode293html
5 blackbody model httpsheasarcgsfcnasagovxanaduxspecmanualnode136html
6 bkn2pow model httpsheasarcgsfcnasagovxanaduxspecmanualnode141html
7 grbcomp model httpsheasarcnasagovdocsxanaduxspecmodelsgrbcomphtml
depending on ratio between γm and the cooling Lorentz
factor γc (Sari et al 1998) We computed the resulting
photon spectrum of population of electrons assuming
that the average electron distribution at a given time is
dNdγ prop γminus2 for γc lt γ lt γm and dNdγ prop γminuspminus1
for γ gt γm in fast cooling regime while dNdγ prop γminusp
for γm lt γ lt γc and dNdγ prop γminuspminus1 for γ gt γc in
slow cooling regime The synchrotron model is made of
four free parameters the ratio between characteristic
Lorentz factors γmγc the peak energy of Fν spectrum
Ec which is simply the energy which corresponds to the
cooling frequency the power-law index of electrons dis-
tribution p and the normalization We built the table
model for the range of 01 le γmγc le 100 and 2 le p le 5
To fit the time integrated spectrum of Episode 1 we
use the four models described above (i) Band (ii) Band
+ blackbody (BB) (iii) broken power law (bkn2pow)
and (iv) the Comptonization model (grbcomp) The
best fit parameters of the tested models are reported
in Table 1 The νFν plots along with the residuals
are shown in Figure 3 for the four models used The
Band fit shows deviations at lower energies signifying
deviations from the power law that is used to model the
spectra from the low energy threshold of 8 keV to the
peak energy of the Band function (sim150 keV) We have
examined these residuals in detail by progressively rais-
ing the low energy threshold to 40 keV (greater than
the energy in which the deviations are seen) and ex-
6 Chand et al
trapolating the model to the low energies The low en-
ergy features could still be seen The presence of such
an anomaly is found in previous studies (Tierney et al
2013) and we conclude that a separate low energy fea-
ture in the spectra can exist We included a blackbody
(BB) along with the Band model for higher energies but
the residuals still show a systematic hump We also tried
another model for this feature of the spectrum a pow-
erlaw with two breaks (bkn2pow model) The bkn2pow
model is preferable as the pgstat is much less for the
same number of parameters (∆pgstat = 41) The pres-
ence of a narrow residual hump also necessitate the need
of a sharper break than a smooth blackbody curvature
This also hints that the break does not evolve much in
time and thus is not smeared out The Comptonization
model (grbcomp) however gives the best fit for the time
integrated spectrum of Episode 1 All the parameters of
this model other than β fbflag and log(A) were left
free The parameter β was frozen to the value 02 to
ignore terms O(sim β2) and fbflag was set to zero to in-
clude only the first order bulk Comptonization term A
value of 39 for γ shows deviation for the seed photons
from the seed blackbody spectrum However during the
time resolved spectral analysis as reported in the next
subsection we kept it fixed to 3 to consider a blackbody
spectrum for the seed photons
The isotropic energy (Eγiso) is calculated in the cos-
mological frame of the GRB by integrating the observed
energy spectrum over 1 keV(1 + z) to 10MeV(1 + z)
The tested models differ significantly only at low en-
ergies and yield similar Eγiso We have Eγiso =
22 times 1053 erg for the best fit model grbcomp The
Γ0 minus Eγ iso correlation between the initial Lorentz fac-
tor and the isotropic energy can be used to estimate Γ0
of the fireball ejecta (Liang et al 2010) The estimated
Γ0 is 392+38minus34 The errors are propagated from the nor-
malization and slope of the correlation The episode 2
could be spectrally well described by a simple power-law
and the best fit power-law index is 190+007minus006 for pgstat
274 for 229 degrees of freedom
41 Parameters evolution
We performed time resolved analysis to capture the
variations in the spectral properties by dividing the data
into time segments based on the Bayesian blocks made
from the 100 - 400 keV light curve We test the models
that were used for the time-integrated analysis The de-
viation from Band spectrum at low energies observed in
the time-integrated spectrum is also present in the time-
resolved bins thus justifying the need to use more com-
plex models than the simple Band function We how-
ever find that the three additional models (Band+BB
bknpwl and grbcomp) represent the time resolved spec-
tral data equally well The evolution of the model pa-
rameters is shown in Figure 4 In Fermi-GBM energy
range 8-20 keV is divided into 12 energy channels and
thus it provided sufficient data points to constrain the
power-law or BB temperature whenever BB peak or low
energy break falls well within these energy channels In
case of bkn2pow the low energy index is very steep
(sim minus3) when the break energy E1 found to be close
to the lower edge of the detection band For such cases
we froze the index to minus3 to obtain constraints on the
other parameters of the model When we fit with the
Band function the peak energy Ep shows three pulse
like structures in their temporal evolution and these can
be identified as showing a hard to soft (HTS) evolution
for peaks in the photon flux The first structure in Ep(at sim10 s) can be associated with the enhancement seen
in the gt1 MeV flux (Figure 2 top panel) When the low
energy feature is modeled using bkn2pow almost all the
peak energies fall below 200 keV The variation in the
low energy break (E1) remains concentrated in a very
narrow band (10 minus 20 keV) The best fit parameters
for all the models are presented in Table 5
The evolution of the derived parameters of grbcomp
model such as photospheric radius (Rph) and bulk pa-
rameter (δ) is shown in Figure 6
411 Distribution of parameters
Despite the fact that the best fit to the time integrated
spectrum is the Comptonization model (grbcomp) we
have tested the models (i) Band (ii) bkn2pow (iii)
BB+Band and (iv) grbcomp for the time resolved spec-
tra The distribution of the parameters is presented in
Figure 7 and are summarized here
For the Band function the low energy index α is dis-
tributed with a mean value minus1 (σ = 013) The maxi-
mum value observed is minus025 for a few time bins and in
the other cases α remains mostly belowminus08 The values
of low energy index agree with what is typically observed
for long GRBs (lt α gt= minus1) which is however known
to be harder than the synchrotron radiation in the fast
cooling regime The high energy index follows a bimodal
distribution with a mean value of minus27 (σ = 03) for the
major chunk concentrated around minus3 lt β lt minus2 and can
be interpreted as values normally observed for GRBs
The peak energy Ep is between 32 keV and 365 keV
with a median sim 140 (σ = 83) keV Its distribution also
shows a bimodal nature which reflects the evolution of
Ep
In the case of bkn2pow we observed that when the
lower break energy E1 is near the lower edge of the
detection band the power-law index below E1 is very
Variable prompt emission polarization in GRB 171010A 7
Table 1 The best fit parameters for the time integrated spectrum of GRB 171010A Episode 1
Model
Band α β Ep (keV) pgstatdof
minus115+001minus001 minus240+003
minus003 163+3minus3 2786335
BB+Band α β Ep (keV) kTBB (keV) pgstatdof
minus075+004minus003 minus240+004
minus003 1500+25minus26 58+01
minus01 1465333
bkn2pow α1 α2 α3 E1 (keV) E2 (keV) pgstatdof
048+006minus007 1464+0006
minus0005 233+002minus002 172+04
minus04 1327+23minus23 1421333
grbcomp kTs (keV) kTe (keV) τ αb Rph (1010 cm) pgstatdof
48+05minus04 55+3
minus3 415+018minus015 152+004
minus004 80+22minus20 1281332
Synchrotron model γmγc Ec (keV) p pgstatdof
406+003minus008 216+02
minus04 gt 482 2520335
steep This is expected because there are only a few
channels here and the fit probably gives an unphysical
result We thus fixed the values to minus3 as they are diffi-
cult to constrain by the fits and also hamper the over-
all fitting process Note that bkn2pow model is defined
with an a-priori negative sign with it and we have to
be cautious while comparing it with the Band function
where the indices are defined without a negative sign
For the purpose of comparison we will explicitly reverse
the signs of the bkn2pow indices The mean value of minusα1
is sim 03(σ = 065) Here we have ignored values gt 15
as they form another part of the bimodal distribution
with low E1 during the time when E1 is near the lower
edge of the GBM energy band The mean value of minusα2
is sim minus14 (σ = 022) This forms the second power law
from E1 to E2 The third segment of the emission has
power law index minusα3 with a mean of sim minus26 (σ = 023)
The low energy break E1 has a mean sim 16 (σ = 23) keV
and it falls in a narrow range of 11 to 20 keV The mean
E2 is sim 140 (σ = 32) keV comparable to the mean of
Band function peak energy with a uni-modal distribu-
tion The E2 values are concentrated in the range 93 to
350 keV
When a blackbody is added the fits have an improved
statistics compared to the Band function throughout
the burst (see Figure 5) The blackbody temperature
vary between 4 minus 10 keV with a median of sim 63(σ =
112) keV The α distribution has harder values while
Ep and β are similar to the distributions of their counter-
parts in the Band function The presence of blackbody
does not seem to move the peak energies significantly
albeit an upward shift is noticeable In the grbcomp
model the average temperature of the seed photons was
68 (σ = 08) keV The electron temperature kTe was
found to be 55 (σ = 21) keV We derived the photo-
spheric radius from the normalization of the model We
found the photospheric radius sim 1011 cm The grbcomp
model parameters are reasonable and a photospheric ra-
dius of 1011 cm is consistent with its predictions (Fron-
tera et al 2013)
412 Correlations of parameters
We explore two parameter correlations and present
the graphs in Figure 8
(i) kTBB vs Ep Thermal components observed in a
set of bright Fermi single pulse GRBs are correlated to
the peak of non-thermal emission (Burgess et al 2014a)
The exponent of the power-law relation (Ep prop T q) indi-
cates the position of the photosphere if it is in the coast-
ing phase or acceleration phase The jet is dominated by
magnetic fields when q is 2 and baryonic if q is nearly 1
However these results were found on GRBs with single
pulses and for GRBs made up of overlapping pulses such
criteria may not be valid For GRB 171010A a positive
correlation (Ep prop T 22) between Ep and kTBB is found
with a log linear Pearson correlation coefficient of 081
p-value sim 10minus15 The index points out therefore a
magnetically dominated jet with photosphere below the
saturation radius We will discuss this result coupled
with the polarization results in Section 7 The peak en-
ergy from Band function and BB + Band function are
also found to be correlated Ep Band prop E12p BB+Band
(ii) Correlations among grbcomp parameters Corre-
lations between grbcomp model parameters and other
model parameters are reported in Frontera et al (2013)
We found a strong correlation between peak energy of
the Band function and the bulk parameter (δ) with
log linear Pearson coefficient and p-value r(p) of -068
(sim 10minus9) The seed photon temperature kTBB and
photospheric radius Rph are uncorrelated contrary to a
strong anti-correlation reported in Frontera et al 2013
The seed blackbody temperature and the electron tem-
perature are not correlated consistent with the pre-
dictions of grbcomp model The parameter kTe and
peak energy of BB + Band model are correlated with
kTe prop E1p BB+Band
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
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6 Chand et al
trapolating the model to the low energies The low en-
ergy features could still be seen The presence of such
an anomaly is found in previous studies (Tierney et al
2013) and we conclude that a separate low energy fea-
ture in the spectra can exist We included a blackbody
(BB) along with the Band model for higher energies but
the residuals still show a systematic hump We also tried
another model for this feature of the spectrum a pow-
erlaw with two breaks (bkn2pow model) The bkn2pow
model is preferable as the pgstat is much less for the
same number of parameters (∆pgstat = 41) The pres-
ence of a narrow residual hump also necessitate the need
of a sharper break than a smooth blackbody curvature
This also hints that the break does not evolve much in
time and thus is not smeared out The Comptonization
model (grbcomp) however gives the best fit for the time
integrated spectrum of Episode 1 All the parameters of
this model other than β fbflag and log(A) were left
free The parameter β was frozen to the value 02 to
ignore terms O(sim β2) and fbflag was set to zero to in-
clude only the first order bulk Comptonization term A
value of 39 for γ shows deviation for the seed photons
from the seed blackbody spectrum However during the
time resolved spectral analysis as reported in the next
subsection we kept it fixed to 3 to consider a blackbody
spectrum for the seed photons
The isotropic energy (Eγiso) is calculated in the cos-
mological frame of the GRB by integrating the observed
energy spectrum over 1 keV(1 + z) to 10MeV(1 + z)
The tested models differ significantly only at low en-
ergies and yield similar Eγiso We have Eγiso =
22 times 1053 erg for the best fit model grbcomp The
Γ0 minus Eγ iso correlation between the initial Lorentz fac-
tor and the isotropic energy can be used to estimate Γ0
of the fireball ejecta (Liang et al 2010) The estimated
Γ0 is 392+38minus34 The errors are propagated from the nor-
malization and slope of the correlation The episode 2
could be spectrally well described by a simple power-law
and the best fit power-law index is 190+007minus006 for pgstat
274 for 229 degrees of freedom
41 Parameters evolution
We performed time resolved analysis to capture the
variations in the spectral properties by dividing the data
into time segments based on the Bayesian blocks made
from the 100 - 400 keV light curve We test the models
that were used for the time-integrated analysis The de-
viation from Band spectrum at low energies observed in
the time-integrated spectrum is also present in the time-
resolved bins thus justifying the need to use more com-
plex models than the simple Band function We how-
ever find that the three additional models (Band+BB
bknpwl and grbcomp) represent the time resolved spec-
tral data equally well The evolution of the model pa-
rameters is shown in Figure 4 In Fermi-GBM energy
range 8-20 keV is divided into 12 energy channels and
thus it provided sufficient data points to constrain the
power-law or BB temperature whenever BB peak or low
energy break falls well within these energy channels In
case of bkn2pow the low energy index is very steep
(sim minus3) when the break energy E1 found to be close
to the lower edge of the detection band For such cases
we froze the index to minus3 to obtain constraints on the
other parameters of the model When we fit with the
Band function the peak energy Ep shows three pulse
like structures in their temporal evolution and these can
be identified as showing a hard to soft (HTS) evolution
for peaks in the photon flux The first structure in Ep(at sim10 s) can be associated with the enhancement seen
in the gt1 MeV flux (Figure 2 top panel) When the low
energy feature is modeled using bkn2pow almost all the
peak energies fall below 200 keV The variation in the
low energy break (E1) remains concentrated in a very
narrow band (10 minus 20 keV) The best fit parameters
for all the models are presented in Table 5
The evolution of the derived parameters of grbcomp
model such as photospheric radius (Rph) and bulk pa-
rameter (δ) is shown in Figure 6
411 Distribution of parameters
Despite the fact that the best fit to the time integrated
spectrum is the Comptonization model (grbcomp) we
have tested the models (i) Band (ii) bkn2pow (iii)
BB+Band and (iv) grbcomp for the time resolved spec-
tra The distribution of the parameters is presented in
Figure 7 and are summarized here
For the Band function the low energy index α is dis-
tributed with a mean value minus1 (σ = 013) The maxi-
mum value observed is minus025 for a few time bins and in
the other cases α remains mostly belowminus08 The values
of low energy index agree with what is typically observed
for long GRBs (lt α gt= minus1) which is however known
to be harder than the synchrotron radiation in the fast
cooling regime The high energy index follows a bimodal
distribution with a mean value of minus27 (σ = 03) for the
major chunk concentrated around minus3 lt β lt minus2 and can
be interpreted as values normally observed for GRBs
The peak energy Ep is between 32 keV and 365 keV
with a median sim 140 (σ = 83) keV Its distribution also
shows a bimodal nature which reflects the evolution of
Ep
In the case of bkn2pow we observed that when the
lower break energy E1 is near the lower edge of the
detection band the power-law index below E1 is very
Variable prompt emission polarization in GRB 171010A 7
Table 1 The best fit parameters for the time integrated spectrum of GRB 171010A Episode 1
Model
Band α β Ep (keV) pgstatdof
minus115+001minus001 minus240+003
minus003 163+3minus3 2786335
BB+Band α β Ep (keV) kTBB (keV) pgstatdof
minus075+004minus003 minus240+004
minus003 1500+25minus26 58+01
minus01 1465333
bkn2pow α1 α2 α3 E1 (keV) E2 (keV) pgstatdof
048+006minus007 1464+0006
minus0005 233+002minus002 172+04
minus04 1327+23minus23 1421333
grbcomp kTs (keV) kTe (keV) τ αb Rph (1010 cm) pgstatdof
48+05minus04 55+3
minus3 415+018minus015 152+004
minus004 80+22minus20 1281332
Synchrotron model γmγc Ec (keV) p pgstatdof
406+003minus008 216+02
minus04 gt 482 2520335
steep This is expected because there are only a few
channels here and the fit probably gives an unphysical
result We thus fixed the values to minus3 as they are diffi-
cult to constrain by the fits and also hamper the over-
all fitting process Note that bkn2pow model is defined
with an a-priori negative sign with it and we have to
be cautious while comparing it with the Band function
where the indices are defined without a negative sign
For the purpose of comparison we will explicitly reverse
the signs of the bkn2pow indices The mean value of minusα1
is sim 03(σ = 065) Here we have ignored values gt 15
as they form another part of the bimodal distribution
with low E1 during the time when E1 is near the lower
edge of the GBM energy band The mean value of minusα2
is sim minus14 (σ = 022) This forms the second power law
from E1 to E2 The third segment of the emission has
power law index minusα3 with a mean of sim minus26 (σ = 023)
The low energy break E1 has a mean sim 16 (σ = 23) keV
and it falls in a narrow range of 11 to 20 keV The mean
E2 is sim 140 (σ = 32) keV comparable to the mean of
Band function peak energy with a uni-modal distribu-
tion The E2 values are concentrated in the range 93 to
350 keV
When a blackbody is added the fits have an improved
statistics compared to the Band function throughout
the burst (see Figure 5) The blackbody temperature
vary between 4 minus 10 keV with a median of sim 63(σ =
112) keV The α distribution has harder values while
Ep and β are similar to the distributions of their counter-
parts in the Band function The presence of blackbody
does not seem to move the peak energies significantly
albeit an upward shift is noticeable In the grbcomp
model the average temperature of the seed photons was
68 (σ = 08) keV The electron temperature kTe was
found to be 55 (σ = 21) keV We derived the photo-
spheric radius from the normalization of the model We
found the photospheric radius sim 1011 cm The grbcomp
model parameters are reasonable and a photospheric ra-
dius of 1011 cm is consistent with its predictions (Fron-
tera et al 2013)
412 Correlations of parameters
We explore two parameter correlations and present
the graphs in Figure 8
(i) kTBB vs Ep Thermal components observed in a
set of bright Fermi single pulse GRBs are correlated to
the peak of non-thermal emission (Burgess et al 2014a)
The exponent of the power-law relation (Ep prop T q) indi-
cates the position of the photosphere if it is in the coast-
ing phase or acceleration phase The jet is dominated by
magnetic fields when q is 2 and baryonic if q is nearly 1
However these results were found on GRBs with single
pulses and for GRBs made up of overlapping pulses such
criteria may not be valid For GRB 171010A a positive
correlation (Ep prop T 22) between Ep and kTBB is found
with a log linear Pearson correlation coefficient of 081
p-value sim 10minus15 The index points out therefore a
magnetically dominated jet with photosphere below the
saturation radius We will discuss this result coupled
with the polarization results in Section 7 The peak en-
ergy from Band function and BB + Band function are
also found to be correlated Ep Band prop E12p BB+Band
(ii) Correlations among grbcomp parameters Corre-
lations between grbcomp model parameters and other
model parameters are reported in Frontera et al (2013)
We found a strong correlation between peak energy of
the Band function and the bulk parameter (δ) with
log linear Pearson coefficient and p-value r(p) of -068
(sim 10minus9) The seed photon temperature kTBB and
photospheric radius Rph are uncorrelated contrary to a
strong anti-correlation reported in Frontera et al 2013
The seed blackbody temperature and the electron tem-
perature are not correlated consistent with the pre-
dictions of grbcomp model The parameter kTe and
peak energy of BB + Band model are correlated with
kTe prop E1p BB+Band
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Gao H amp Zhang B 2015 ApJ 801 103
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Izzo L Ruffini R Penacchioni A V et al 2012 AampA
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Komatsu E Dunkley J Nolta M R et al 2009 ApJS
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Lloyd N M amp Petrosian V 2000 ApJ 543 722
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Meszaros P amp Rees M J 1993 ApJ 405 278
Meszaros P amp Rees M J 1997 ApJ 476 232
Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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Molinari E Vergani S D Malesani D et al 2007
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Narayan R Paczynski B amp Piran T 1992 ApJL 395
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Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
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Oganesyan G Nava L Ghirlanda G amp Celotti A
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Page K L Starling R L C Fitzpatrick G et al 2011
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Poolakkil S amp Meegan C 2017 GRB Coordinates
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Ravasio M E Oganesyan G Ghirlanda G et al 2018
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processes in astrophysics
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Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Scargle J D Norris J P Jackson B amp Chiang J 2013
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Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
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Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
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amp Zhang B 2016 ApJ 816 72
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Nature Astronomy 2 69
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751 90
Variable prompt emission polarization in GRB 171010A 7
Table 1 The best fit parameters for the time integrated spectrum of GRB 171010A Episode 1
Model
Band α β Ep (keV) pgstatdof
minus115+001minus001 minus240+003
minus003 163+3minus3 2786335
BB+Band α β Ep (keV) kTBB (keV) pgstatdof
minus075+004minus003 minus240+004
minus003 1500+25minus26 58+01
minus01 1465333
bkn2pow α1 α2 α3 E1 (keV) E2 (keV) pgstatdof
048+006minus007 1464+0006
minus0005 233+002minus002 172+04
minus04 1327+23minus23 1421333
grbcomp kTs (keV) kTe (keV) τ αb Rph (1010 cm) pgstatdof
48+05minus04 55+3
minus3 415+018minus015 152+004
minus004 80+22minus20 1281332
Synchrotron model γmγc Ec (keV) p pgstatdof
406+003minus008 216+02
minus04 gt 482 2520335
steep This is expected because there are only a few
channels here and the fit probably gives an unphysical
result We thus fixed the values to minus3 as they are diffi-
cult to constrain by the fits and also hamper the over-
all fitting process Note that bkn2pow model is defined
with an a-priori negative sign with it and we have to
be cautious while comparing it with the Band function
where the indices are defined without a negative sign
For the purpose of comparison we will explicitly reverse
the signs of the bkn2pow indices The mean value of minusα1
is sim 03(σ = 065) Here we have ignored values gt 15
as they form another part of the bimodal distribution
with low E1 during the time when E1 is near the lower
edge of the GBM energy band The mean value of minusα2
is sim minus14 (σ = 022) This forms the second power law
from E1 to E2 The third segment of the emission has
power law index minusα3 with a mean of sim minus26 (σ = 023)
The low energy break E1 has a mean sim 16 (σ = 23) keV
and it falls in a narrow range of 11 to 20 keV The mean
E2 is sim 140 (σ = 32) keV comparable to the mean of
Band function peak energy with a uni-modal distribu-
tion The E2 values are concentrated in the range 93 to
350 keV
When a blackbody is added the fits have an improved
statistics compared to the Band function throughout
the burst (see Figure 5) The blackbody temperature
vary between 4 minus 10 keV with a median of sim 63(σ =
112) keV The α distribution has harder values while
Ep and β are similar to the distributions of their counter-
parts in the Band function The presence of blackbody
does not seem to move the peak energies significantly
albeit an upward shift is noticeable In the grbcomp
model the average temperature of the seed photons was
68 (σ = 08) keV The electron temperature kTe was
found to be 55 (σ = 21) keV We derived the photo-
spheric radius from the normalization of the model We
found the photospheric radius sim 1011 cm The grbcomp
model parameters are reasonable and a photospheric ra-
dius of 1011 cm is consistent with its predictions (Fron-
tera et al 2013)
412 Correlations of parameters
We explore two parameter correlations and present
the graphs in Figure 8
(i) kTBB vs Ep Thermal components observed in a
set of bright Fermi single pulse GRBs are correlated to
the peak of non-thermal emission (Burgess et al 2014a)
The exponent of the power-law relation (Ep prop T q) indi-
cates the position of the photosphere if it is in the coast-
ing phase or acceleration phase The jet is dominated by
magnetic fields when q is 2 and baryonic if q is nearly 1
However these results were found on GRBs with single
pulses and for GRBs made up of overlapping pulses such
criteria may not be valid For GRB 171010A a positive
correlation (Ep prop T 22) between Ep and kTBB is found
with a log linear Pearson correlation coefficient of 081
p-value sim 10minus15 The index points out therefore a
magnetically dominated jet with photosphere below the
saturation radius We will discuss this result coupled
with the polarization results in Section 7 The peak en-
ergy from Band function and BB + Band function are
also found to be correlated Ep Band prop E12p BB+Band
(ii) Correlations among grbcomp parameters Corre-
lations between grbcomp model parameters and other
model parameters are reported in Frontera et al (2013)
We found a strong correlation between peak energy of
the Band function and the bulk parameter (δ) with
log linear Pearson coefficient and p-value r(p) of -068
(sim 10minus9) The seed photon temperature kTBB and
photospheric radius Rph are uncorrelated contrary to a
strong anti-correlation reported in Frontera et al 2013
The seed blackbody temperature and the electron tem-
perature are not correlated consistent with the pre-
dictions of grbcomp model The parameter kTe and
peak energy of BB + Band model are correlated with
kTe prop E1p BB+Band
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Chattopadhyay T Vadawale S V Aarthy E et al
2017 ArXiv e-prints arXiv170706595
Covino S amp Gotz D 2016 Astronomical and
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DrsquoAi A Melandri A Sbarufatti B et al 2017 GRB
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Dai Z G amp Lu T 1998 AampA 333 L87
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Evans P A 2017 GRB Coordinates Network Circular
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Frail D A Kulkarni S R Sari R et al 2001 ApJL
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Frederiks D Golenetskii S Aptekar R et al 2017 GRB
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Frontera F Amati L Farinelli R et al 2013 ApJ 779
175
Gao H amp Zhang B 2015 ApJ 801 103
Guiriec S Connaughton V Briggs M S et al 2011
ApJL 727 L33
Izzo L Ruffini R Penacchioni A V et al 2012 AampA
543 A10
Kankare E OrsquoNeill D Izzo L et al 2017 GRB
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1-2018 (2017) 22002
Komatsu E Dunkley J Nolta M R et al 2009 ApJS
180 330
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Lazzati D Ghisellini G Celotti A amp Rees M J 2000
ApJL 529 L17
Liang E-W Yi S-X Zhang J et al 2010 ApJ 725
2209
Lloyd N M amp Petrosian V 2000 ApJ 543 722
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e-prints arXiv161101451
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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Molinari E Vergani S D Malesani D et al 2007
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Narayan R Paczynski B amp Piran T 1992 ApJL 395
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Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
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Oganesyan G Nava L Ghirlanda G amp Celotti A
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Page K L Starling R L C Fitzpatrick G et al 2011
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Poolakkil S amp Meegan C 2017 GRB Coordinates
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Ravasio M E Oganesyan G Ghirlanda G et al 2018
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Rees M J amp Meszaros P 1992 MNRAS 258 41P
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Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
8 Chand et al
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
01
1
10
100
1000
νF
ν (
keV
cm
minus2 s
minus1)
n8
nb
b1
10 100 1000 104
minus10
0
10
Resid
uals
Energy (keV)
Figure 3 The time integrated νFν plot of Episode 1 of GRB 171010A (-5 s to 246 s) along with the best fit models Residualsto the fit are shown in the bottom panels The Band model (top left) shows a low energy feature and can be either modeled by ablackbody (top right) or by adding another powerlaw at the low energy (middle left) The best fit model is the Comptonizationmodel grbcomp (middle right) The synchrotron model is shown in bottom panel
5 AFTERGLOWS
We have analyzed the afterglow data of GRB 171010A
in gamma-rays (Fermi-LAT) and X-rays (Swift-XRT)
and the results are shown in Figure 9 and 10
51 γ-ray afterglows
A 12 region of interest (ROI) was selected around the
refined Swift-XRT coordinates and an angle of 100 be-
tween the GRB direction and Fermi zenith was selected
based on the navigation plots The zenith cut is ap-
plied to reduce the contamination from γ-rays of Earth
albedo Transient event class and its instrument re-
sponse function P8R2 TRANSIENT020E V 6 is used
as it is appropriate for GRB durations Details about
LAT analysis methods and procedures can be found in
the Fermi-LAT GRB catalog (Ackermann et al 2013)
A simple power-law temporal decay is observed for the
LAT light curve with a hint of momentary increase or
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Chattopadhyay T Vadawale S V Aarthy E et al
2017 ArXiv e-prints arXiv170706595
Covino S amp Gotz D 2016 Astronomical and
Astrophysical Transactions 29 205
DrsquoAi A Melandri A Sbarufatti B et al 2017 GRB
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Dai Z G amp Lu T 1998 AampA 333 L87
Deng W Zhang H Zhang B amp Li H 2016 ApJL 821
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Evans P A 2017 GRB Coordinates Network Circular
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Frail D A Kulkarni S R Sari R et al 2001 ApJL
562 L55
Frederiks D Golenetskii S Aptekar R et al 2017 GRB
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1-2018 (2017) 22003
Frontera F Amati L Farinelli R et al 2013 ApJ 779
175
Gao H amp Zhang B 2015 ApJ 801 103
Guiriec S Connaughton V Briggs M S et al 2011
ApJL 727 L33
Izzo L Ruffini R Penacchioni A V et al 2012 AampA
543 A10
Kankare E OrsquoNeill D Izzo L et al 2017 GRB
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1-2018 (2017) 22002
Komatsu E Dunkley J Nolta M R et al 2009 ApJS
180 330
Lazzati D amp Begelman M C 2009 ApJL 700 L141
Lazzati D Ghisellini G Celotti A amp Rees M J 2000
ApJL 529 L17
Liang E-W Yi S-X Zhang J et al 2010 ApJ 725
2209
Lloyd N M amp Petrosian V 2000 ApJ 543 722
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e-prints arXiv161101451
Meszaros P amp Rees M J 1993 ApJ 405 278
Meszaros P amp Rees M J 1997 ApJ 476 232
Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
mdash 1999 MNRAS 306 L39
Molinari E Vergani S D Malesani D et al 2007
AampA 469 L13
Narayan R Paczynski B amp Piran T 1992 ApJL 395
L83
Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
642 389
Oganesyan G Nava L Ghirlanda G amp Celotti A
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Omodei N Vianello G amp Ahlgren B 2017 GRB
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Page K L Starling R L C Fitzpatrick G et al 2011
MNRAS 416 2078
Poolakkil S amp Meegan C 2017 GRB Coordinates
Network Circular Service No 21992 1-2018 (2017)
21992
Ravasio M E Oganesyan G Ghirlanda G et al 2018
AampA 613 A16
Rees M J amp Meszaros P 1992 MNRAS 258 41P
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Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 9
Figure 4 Upper Left The evolution of peak energy and the low energy spectral index of the Band model fit to time resolvedspectra The low energy spectral indices lie between fast and slow cooling limits of synchrotron radiation (indicated by dottedline and dot-dashed line respectively) Intervals used for polarization measurement are segregated by vertical dottedlines to guide the eye The photon flux is shown as a grey histogram (right hand side scale) Upper Right The evolution ofpeak energy blackbody temperature and low energy index when the low energy anomaly seen in the Band function fit is modeledby an additional blackbody Low energy indices are now above the slow cooling limit but below the limit of jitter radiation(black solid line) Lower Left The Evolution of two break energies and indices for a broken power law fit The index minusα2 inthis case shifts closer to the fast cooling line or even softer than this limit The energy index α1 below the low energy breakis harder with a median value 13 The break energy is also low and falls in the range between 15 - 25 keV Bottom Right Evolution of electron temperature seed photon temperature and high energy index αbf of the Comptonization model grbcomp
0 20 40 60 80 100 120 140 160t
06
08
10
12
14
16
18
20
pgst
atD
OF
bkn2powBandGRBCOMPBB + BandSynchrotron
Figure 5 The variation of the statistic pgstat with time A low energy break is preferable in almost all the bins All threemodels BB+Band bkn2pow synchrotron and grbcomp have comparable pgstat values and provide acceptable fits to the data inthe time-resolved analysis However in time-averaged analysis the grbcomp model provides the best fit
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Chattopadhyay T Vadawale S V Aarthy E et al
2017 ArXiv e-prints arXiv170706595
Covino S amp Gotz D 2016 Astronomical and
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DrsquoAi A Melandri A Sbarufatti B et al 2017 GRB
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Dai Z G amp Lu T 1998 AampA 333 L87
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Evans P A 2017 GRB Coordinates Network Circular
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Frail D A Kulkarni S R Sari R et al 2001 ApJL
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Frederiks D Golenetskii S Aptekar R et al 2017 GRB
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Frontera F Amati L Farinelli R et al 2013 ApJ 779
175
Gao H amp Zhang B 2015 ApJ 801 103
Guiriec S Connaughton V Briggs M S et al 2011
ApJL 727 L33
Izzo L Ruffini R Penacchioni A V et al 2012 AampA
543 A10
Kankare E OrsquoNeill D Izzo L et al 2017 GRB
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1-2018 (2017) 22002
Komatsu E Dunkley J Nolta M R et al 2009 ApJS
180 330
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Lazzati D Ghisellini G Celotti A amp Rees M J 2000
ApJL 529 L17
Liang E-W Yi S-X Zhang J et al 2010 ApJ 725
2209
Lloyd N M amp Petrosian V 2000 ApJ 543 722
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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Molinari E Vergani S D Malesani D et al 2007
AampA 469 L13
Narayan R Paczynski B amp Piran T 1992 ApJL 395
L83
Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
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Oganesyan G Nava L Ghirlanda G amp Celotti A
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Page K L Starling R L C Fitzpatrick G et al 2011
MNRAS 416 2078
Poolakkil S amp Meegan C 2017 GRB Coordinates
Network Circular Service No 21992 1-2018 (2017)
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Ravasio M E Oganesyan G Ghirlanda G et al 2018
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Rees M J amp Meszaros P 1992 MNRAS 258 41P
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Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
10 Chand et al
0 25 50 75 100 125 150t (s)
10
15
20
25
30
35
40R p
h(1
011 c
m)
0 25 50 75 100 125 150t (s)
1
2
3
4
5
6
7
Figure 6 The evolution of the photospheric radius (upperpanel) and the bulk parameter (lower panel) obtained fromthe grbcomp model
steady emission in both energy and photon fluxes during
the first and second time bins 346minus 514 s amp 514minus 635
s The LAT photon flux varies with time as a power law
with an index minus156 plusmn 040 and the energy flux variesas a power law with an index minus137plusmn 045 The photon
index of LAT-HE is ΓL = minus20 plusmn 01 from a spectral
fit obtained by fitting the first 105 sec data This gives
spectral index βL = ΓL + 1 to be minus10plusmn 01 The time
resolved spectra do not show variation in the photon
index in the first four bins
In the external shock model for ν gt maxνm νcwhich is generally true for reasonable shock parame-
ters we can derive the power law index of the shocked
electrons by fν prop νminusp2 We have synchrotron energy
flux fL prop νminusβLtminusαL (see the LAT lightcurve in Figure
9) We found αL = 137 plusmn 045 and βL = 10 plusmn 01
The value of βL gives us p = 20 plusmn 02 Thus the
power-law index for the energy flux decay can be pre-
dicted by using fL prop t(2minus3p)4 The calculated value of
αL is minus10 plusmn 02 which agrees well with the observed
value of minus137 plusmn 045 Hence we can conclude that
for GRB 171010A the LAT high energy afterglows are
formed in an external forward shock
For the thin shell case in a homogeneous medium and
assuming that the peak of the LAT afterglow (tp) occurs
either before or in the second time bin gives tp lt 530 s
and we can constrain the initial Lorentz factor (Γ0) of
the GRB jet (see eg Sari amp Piran 1999 Molinari et al
2007) using
Γ0 gt 193(nη)minus18 times
(Eγ52t3pz2
)18
(3)
where mp is the mass of proton η is the radiation
efficiency tp is the time when afterglow peaks Eγ52is the k corrected rest frame energy of the GRB in
the 1 minus 10 000 keV band For a typical density
n = 01 cmminus3 of homogeneous ambient medium and
η = 05 we can constrain the initial Lorentz factor
Γ0 gt 330 This limit is consistent with Γ0 found in
Section 4 from Γ0 minus Eγ iso correlation
The photon index hardens in the 2150 minus 6650 s time
bin and the flux also seems to deviate from the power
law fit This hints at a contribution from an inverse
Compton component The highest energy photon with
a rest frame energy of sim 25 GeV is also observed during
this interval
52 X-ray afterglows
The primary goal of the Swift satellite is to detect
GRBs and observe the afterglows in X-ray and optical
wavelengths If a GRB is not detected by Swift but is de-
tected by some other mission (like Fermi etc) target of
opportunity (ToO) mode observations can be initiated in
Swift for very bright bursts For such bursts the prompt
phase is missed by Swift and afterglow observations arealso inevitably delayed However the detection of X-ray
afterglows with Swift-XRT not only allows us to study
the delayed afterglow emissions but also to precisely lo-
calize the GRB for further ground and space based ob-
servations at longer wavelengths The X-ray afterglow of
GRB 171010A was observed by Swift sim 24300 s (sim 03
days) after the burst We have used the XRT prod-
ucts and lightcurves from the XRT online repository8 to
study the light curve and spectral characteristics The
statistically preferred fit to the count rate light curve in
the 03 minus 10 keV band has three power-law segments
with two breaks The temporal power-law indices and
the break times in the light curve as given in the GRB
online repository are listed in Table 3 The data are also
8 httpwwwswiftacukxrt productsindexphp
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Chattopadhyay T Vadawale S V Aarthy E et al
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175
Gao H amp Zhang B 2015 ApJ 801 103
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ApJL 727 L33
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543 A10
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Komatsu E Dunkley J Nolta M R et al 2009 ApJS
180 330
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ApJL 529 L17
Liang E-W Yi S-X Zhang J et al 2010 ApJ 725
2209
Lloyd N M amp Petrosian V 2000 ApJ 543 722
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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Molinari E Vergani S D Malesani D et al 2007
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Narayan R Paczynski B amp Piran T 1992 ApJL 395
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Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
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Oganesyan G Nava L Ghirlanda G amp Celotti A
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Page K L Starling R L C Fitzpatrick G et al 2011
MNRAS 416 2078
Poolakkil S amp Meegan C 2017 GRB Coordinates
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Ravasio M E Oganesyan G Ghirlanda G et al 2018
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Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 11
1 0Band
0
10
20
Num
ber -102
100 200 300 400Ep Band
14125
75 50 25Band
-277
1 0BB + Band
0
5
10
15
Num
ber -046
100 200 300 400Ep BB + Band
14169
75 50 25 00BB + Band
-265
20 403kTBB + Band
1826
1 02 bkn2pow
00
25
50
75
100
Num
ber -14
100 200 300 400E2 bkn2pow
13446
75 50 25 003 bkn2pow
-255
20 40E1 bkn2pow
156
100 200 300 4003kTe grbcomp
00
25
50
75
100
Num
ber 16567
20 403kTs grbcomp
0
5
10
15
20
Num
ber 2077
Figure 7 The distributions of best-fit parameters for Band bkn2pow and grbcomp models Each histogram consists of ten binsbetween minimum and maximum values Thick vertical dot-dashed lines represent the median of the observed distribution ofthe parameters
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
12 Chand et al
1026 times 101 2 times 102 3 times 102
Ep BB + Band (keV)
102
103
E pB
and (
keV)
1014 times 100 6 times 100
kTBB BB + Band (keV)
102
103
E pB
B+
Ban
d (
keV)
102
Ep BB + Band (keV)
101
102
grbc
omp
kTe
(keV
)
101 2 times 101
E1 (keV)
102
103
E 2 (
keV)
102
2 times 100
3 times 100
4 times 100
6 times 100
E pB
and (
keV)
1014 times 100 6 times 100
kTs (keV)
101
102
kTe
(keV
)
1014 times 100 6 times 100
kTs (keV)
1011
2 times 1011
3 times 1011
4 times 1011
R ph
(cm
)
Figure 8 Correlations obtained for various model parameters and derived parameters
Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Variable prompt emission polarization in GRB 171010A 13
consistent with 3 breaks (Table 3) The light curve with
three breaks resembles the canonical GRB light curves
observed in XRT (Zhang et al 2006 Nousek et al 2006)
We have analysed the XRT spectral data and generated
the energy flux light curve shown in Figure 10 The flux
light curve in the 03 - 10 keV energy band is fit with
a single powerlaw and a broken powerlaw with a single
break at time tb The best fit single powerlaw shows
a decay index of fX prop tminus144plusmn003 while in the bro-
ken powerlaw the pre- and post-break decay indices are
129 plusmn 005 and 197 plusmn 024 respectively with the break
at tb = (337 plusmn 103) times 105 s These values are consis-
tent with the fits for the count rate light curves given in
Table 3
We name the two segments of the light curve with
three breaks as phase 1 (see Table 3) before tb2 and
phase 2 after tb2 The phase 1 is subjectively divided
into 3 time bins to track the evolution of spectral pa-
rameters during this phase The phase 2 is also divided
at the tb3 for inspecting the spectral change with the
apparent rise in the light curve after this point
We froze the equivalent hydrogen column density (nH)
to its Galactic value (Willingale et al 2013) Another
absorption model tbabs in XSPEC is used to model
intrinsic absorption and nH corresponding to it is frozen
to the value obtained from the time integrated fit A
simple power law fits the spectrum for both the phases
The photon index in the XRT band is found to be
ΓX = minus19 plusmn 01 for phase 1 and ΓX = minus17+03minus06 for
phase 2 The evolution of energy flux in 03 minus 10 keV
and the photon index are shown in Figure 10 Similar
to LAT it also predicts p sim 2 when both νm and νcevolve to energies that lie below the XRT band If we
consider p sim 22 (See eg Zhang et al 2006 Nousek
et al 2006) which will be nearly consistent with the
p inferred from LAT afterglow and also near to XRT-
afterglow value Thus for the late time decay we have
αX sim minus115 When the light curve is modeled by a bro-
ken power-law we get fX prop tminus129plusmn005 before the break
and fX prop tminus197plusmn024 thereafter Therefore predicted
αX sim minus115 is nearly consistent with αX sim 129plusmn 005
(three times the error bar) The αX before and after
the break are consistent with the late time decay in the
external shock model And the break observed can be
identified as a jet break (tbreak = 34times 105 s) and used
for finding the opening angle (θj) of the jet as given by
Eq 4 (Frail et al 2001) However an achormatic break
at all wavelengths in the lightcurves is required to claim
it as a jet break The absence of a break till the last
data point observed in XRT can also be utilized to put
a lower limit on the jet break (see for example Wang
et al 2018) So any break before corresponding to last
data point in XRT will also respect that limit because
for a given initial Lorentz factor (Γ0) the jet break will
occur later for a wider jet
θj asymp 0057
(tj
86 400 s
)38(1 + z
2
)minus38(Eiso
1053 erg
)minus18 ( η
02
)18 ( n
01 cmminus3
)18(4)
We get θj = 011 rad (= 63) by using eq 4 The
beaming angle can be estimated by using Lorentz fac-
tor Γ0 using θbeam = 1Γ0 For Γ0 = 330 we have
θbeam = 0003 rad (= 017) Thus we have a wide
bright jet with a narrow beaming angle The Lorentz
factor estimated above is for the final merged shells
propagating to the circum-burst medium (CBM) and
forming an external shock The Lorentz factor for indi-
vidual shells can even be higher than our estimate The
jet energy corrected for collimation is 137times 1051 erg
6 POLARIZATION MEASUREMENTS
GRB 171010A is one of the brightest GRBs detected
in CZTI with an observed fluence gt 10minus4 ergcm2 This
makes the GRB one of potential candidates for polariza-
tion measurement CZTI works as a Compton polarime-
ter where polarization is estimated from the azimuthal
angle distribution of the Compton scattering events be-
tween the CZTI pixels at energies beyond 100 keV
Polarization measurement capability of CZTI has been
demonstrated experimentally during its ground calibra-
tion (Chattopadhyay et al 2014 Vadawale et al 2015)
First on board verification of its X-ray polarimetry mea-
surement capability came with the detection of high po-
larization in Crab in 100 mdash 380 keV (Vadawale et al
2017) Crab was observed for sim 800 ks in two years
after its launch and this was statistically the most sig-
nificant polarization measurement till date in hard X-
rays Polarimetric sensitivity of CZTI for off-axis GRBs
is expected to be less than that for ON-axis sources
(eg Crab) but the high signal to background ratio
for GRBs and availability of pre-GRB and post-GRB
background makes CZTI equally sensitive to polariza-
tion measurements of GRBs Recently we reported sys-
tematic polarization measurement for 11 GRBs with
sim3σ detection for 5 GRBs andsim2σ detection for 1 GRB
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
642 389
Oganesyan G Nava L Ghirlanda G amp Celotti A
2017 ApJ 846 137
mdash 2018 AampA 616 A138
Omodei N Vianello G amp Ahlgren B 2017 GRB
Coordinates Network Circular Service No 21985
1-2018 (2017) 21985
Page K L Starling R L C Fitzpatrick G et al 2011
MNRAS 416 2078
Poolakkil S amp Meegan C 2017 GRB Coordinates
Network Circular Service No 21992 1-2018 (2017)
21992
Ravasio M E Oganesyan G Ghirlanda G et al 2018
AampA 613 A16
Rees M J amp Meszaros P 1992 MNRAS 258 41P
mdash 1994 ApJL 430 L93
Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
14 Chand et al
103 104 105
Time(s)
102
103
104
Ener
gy(M
eV) pgt09
09gtpgt0808gtpgt0707gtpgt0606gtpgt0505gtp
103 104 105
10 10
10 9
10 8
10 7
10 6
10 5
Flux
LAT energy flux (01-10 GeV erg cm 2 s 1)LAT photon flux (01-10 GeV ph cm 2 s 1)
103 104 105
Time since GBM trigger (s)
252015
L
Figure 9 Top panel Energies of individual Fermi-LAT photons (gt 100 MeV) detected more than 345 s after the triggerThe color and transparency of circles depend on the probability (p) of their association with source Middle panel Fermi-LATphoton and energy fluxes in 01 mdash 10 GeV range The photon index in the first time bin was fixed to minus2 to get an upper limiton the fluxes The dashed curve in the background shows the evolution of the LAT photon flux assuming a constant photonindex minus2 The photon flux rises fast initially peaks at sim 530 s and then declines This flux peak was used to obtain a lowerlimit on the Lorentz factor of the ejecta (sect4) Bottom panel Photon indices for FermiLAT in the 01 mdash 10 GeV range
and upper limit estimation for the remaining 5 GRBs
GRB 171010A is a bright GRB registering around sim2000 Compton events in CZTI It is the second bright-
est GRB in terms of number of Compton events after
GRB 160821A and therefore is a potential candidate
for polarization analysis
The details of the method of polarization measure-
ment of GRBs with CZTI can be found in Chattopad-
hyay et al (2017) Here we briefly describe the different
steps involved in the analysis procedure
bull The first step is to identify and select the valid
Compton events We select the double pixel events
during the prompt emission by identifying events
happening within a 40 micros time window The dou-
ble pixel events are then filtered against various
Compton kinematics criteria to finally obtain the
Compton scattered events
bull The selection of Compton events is confined within
the 3times3 pixel block of CZTI modules which re-sults in an 8 bin azimuthal scattering angle dis-
tribution We compute the azimuthal scattering
angles for events during both the GRB prompt
emission and the background before and after
the prompt emission The combined pre and
post-GRB azimuthal distribution is used for back-
ground subtraction to finally obtain the azimuthal
distribution for the GRB
bull The background corrected prompt emission az-
imuthal distribution shows some modulation due
to (a) asymmetry in the solid angles subtended
by the edge and the corner pixels to the central
scattering pixel and (b) the off-axis viewing angle
of the burst These two factors are corrected by
normalizing the azimuthal angle distribution with
a simulated distribution for the same GRB spec-
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 15
105 106
10 13
10 12
10 11
Flux
(er
g cm
2 s
1 )
105 106
Time since GBM trigger (s)
2
1
X
Figure 10 Swift-XRT energy flux in the range 03 - 10 keV(upper panel) A single power law fit (red dotted line) tothe flux gives fX prop tminus144plusmn003 When a break is introducedat tb (red solid line) the powerlaw indices are 129 plusmn 005and 197plusmn024 before and after the break respectively Thebreak observed is at (337plusmn103)times105 s The photon indicesfor the Swift-XRT spectra are shown in the bottom panel
tra at the same off-axis angle assuming the GRB
is completely unpolarized The simulation is per-
formed in Geant4 with a full mass model of CZTI
and AstroSat
bull We fit background and geometry corrected az-
imuthal angle distribution using MCMC simula-
tion to estimate the modulation factor and polar-
ization angle (in CZTI plane) This is followed up
by detailed statistical tests to determine whether
the GRB is truly polarized or not This is an im-
portant step particularly because there can be
systematic effects which can produce significant
modulation in the azimuthal angle distribution
even for completely unpolarized photons These
effects are even more prominent in cases where the
GRB is not very bright
bull If the statistical tests suggest that the GRB is
truly polarized we estimate the polarization frac-
tion by normalizing the fitted modulation fac-
tor with micro100 which is the modulation factor for
100 polarized photons obtained by simulating
the GRB simulated in Geant4 with the AstroSat
mass model If the GRB is found to be unpolar-
ized we estimate the upper limit of polarization
(see Chattopadhyay et al (2017))
275 300 325 350 375 400 425Time + 245357750 sec
20
40
60
80
Coun
tsb
in (
Com
pton
)
Figure 11 Observed Compton event light curve forGRB 171010A in 100 mdash 300 keV band with 1 second binningThe events in the time interval between 300mdash370 seconds inthe light curve are used for polarization analysis
Figure 12 The background subtracted and geometry cor-rected modulation curve for GRB 171010A in 100 mdash 300 keVThe blue solid line is the sinusoidal fit to the modulationcurve We find no clear sinusoidal variation in the azimuthalangle distribution
Figure 11 shows the light curve of GRB 171010A in
Compton events in 100 mdash 300 keV The burst is clearly
seen in Compton events We used a total of 747 sec-
onds of background before and after the burst for the
final background estimation After background subtrac-
tion the number of Compton events during the prompt
emission is found to be sim 2000 Figure 12 shows the
modulation curve in the 100 mdash 300 keV band follow-
ing background subtraction and geometry correction as
discussed in the last section We do not see any clear
sinusoidal modulation in the azimuthal angle distribu-
tion Figure 13 shows the corresponding contour plot
for GRB 171010A Both polarization fraction and an-
gle are poorly constrained signifying that the burst is
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Chattopadhyay T Vadawale S V Aarthy E et al
2017 ArXiv e-prints arXiv170706595
Covino S amp Gotz D 2016 Astronomical and
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DrsquoAi A Melandri A Sbarufatti B et al 2017 GRB
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Frail D A Kulkarni S R Sari R et al 2001 ApJL
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Gao H amp Zhang B 2015 ApJ 801 103
Guiriec S Connaughton V Briggs M S et al 2011
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543 A10
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Komatsu E Dunkley J Nolta M R et al 2009 ApJS
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Lazzati D amp Begelman M C 2009 ApJL 700 L141
Lazzati D Ghisellini G Celotti A amp Rees M J 2000
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Liang E-W Yi S-X Zhang J et al 2010 ApJ 725
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Lloyd N M amp Petrosian V 2000 ApJ 543 722
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
mdash 1999 MNRAS 306 L39
Molinari E Vergani S D Malesani D et al 2007
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Narayan R Paczynski B amp Piran T 1992 ApJL 395
L83
Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
642 389
Oganesyan G Nava L Ghirlanda G amp Celotti A
2017 ApJ 846 137
mdash 2018 AampA 616 A138
Omodei N Vianello G amp Ahlgren B 2017 GRB
Coordinates Network Circular Service No 21985
1-2018 (2017) 21985
Page K L Starling R L C Fitzpatrick G et al 2011
MNRAS 416 2078
Poolakkil S amp Meegan C 2017 GRB Coordinates
Network Circular Service No 21992 1-2018 (2017)
21992
Ravasio M E Oganesyan G Ghirlanda G et al 2018
AampA 613 A16
Rees M J amp Meszaros P 1992 MNRAS 258 41P
mdash 1994 ApJL 430 L93
Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
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Nature Astronomy 2 69
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751 90
16 Chand et al
Figure 13 Contour plot of polarization angle and fractionfor GRB 171010A in 100 mdash 300 keV as obtained from theMCMC method The red green and blue represent the 68 90 and 99 confidence levels respectively
either unpolarized or polarization fraction is below the
sensitivity level of CZTI
In order to verify this we measure Bayes factor for
sinusoidal (for polarized photons) and constant model
(unpolarized photons) by utilizing lsquoThermodynamic In-
tegrationrsquo method on the MCMC parameter space (for
details refer to Chattopadhyay et al (2017)) This yields
a value less than 2 which is assumed to be the threshold
value of Bayes factor for claiming detection of polariza-
tion We therefore estimate the upper limit of polar-
ization for GRB 171010A which is done in two steps
First step involves estimation of polarization detection
threshold (Pthr) by limiting the probability of false de-
tection (to 005 for sim2σ or 001 for sim3σ) The false po-
larization detection probability is estimated by simulat-
ing GRB 171010A for the observed number of Compton
and background events with 100 unpolarized photons
The second step involves measurement of the probabil-
ity of detection of polarization such that probability of
detection of a certain level of polarization (Pupper) being
greater than the polarization detection threshold (Pthr)
is ge 05 (see Chattopadhyay et al (2017) for more de-
tails) The 2σ upper limit (5 of false detection proba-
bility) for GRB 171010A is found to besim42 It is to be
noted that in the sample of bursts used for polarization
analysis in Chattopadhyay et al (2017) GRB 160821A
was found to possess maximum number of Compton
events (sim 2500) The next brightest burst was GRB
160623A with sim 1400 Compton events We estimated
sim 50 polarization at gt 3σ detection significance for
GRB 160821A In comparison GRB 171010A is found
to have sim 2000 Compton events The GRB is detected
at an off-axis angle of 55 We expect CZTI to have sig-
nificant polarmetric sensitivity at such off-axis angles
Therefore polarization for this GRB should be detected
at a significant detection level provided the GRB is at
least sim50 polarized This is consistent to our estima-
tion of 2σ polarization upper limit of sim42
This is an interesting result considering the fact that
the spectral analysis suggests the time integrated peak
energy for all the models is less than 200 keV which falls
within the energy range of polarization analysis There-
fore in order to see the variation of polarization below
and above the peak energy we estimate polarization in
two different energy ranges mdash 100 mdash 200 keV and 200
mdash 300 keV (see Figure 14) There is no clear modulation
at the lower energies whereas we see a sinusoidal varia-
tion in the modulation curve in 200 mdash 300 keV which
is beyond the peak energy of the GRB However it is
to be noted that the Bayes factors for both the energy
ranges are less than 2 signifying that there is no firm
detection of polarization The modulation at higher en-
ergies therefore is just a hint of polarization which is
still an interesting result
One major difference between GRB 160821A (or GRB
160802A GRB 160910A (Chattopadhyay et al 2017))
and GRB 171010A is that the later lasts longer and has
multiple pulses We also see significant variation of peak
energy with time (see Figure 4) These pulses might ex-
hibit different polarization signatures resulting in a net
zero or low polarization when integrated in time We
therefore divided the whole burst in 3 different time in-
tervals mdash 0 mdash 20 seconds 20 mdash 28 seconds and 28 mdash
70 seconds where lsquo0rsquo is the onset of the burst Since
we have already seen a hint of polarization signature in
200 mdash 300 keV we further divided the signals in 100 mdash
200 keV and 200 mdash 300 keV Figure 15 shows the vari-
ation of polarization fraction (middle panel) and po-
larization angle (bottom panel) in three time intervals
for 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
The errors in polarization angle in the first two inter-
vals in both the energy ranges are quite large with no
significant modulation in azimuthal angle distribution
consistent to being unpolarized This is independently
verified with the estimation of low values of Bayes fac-
tor The third interval on the other hand shows high
polarization fraction with a very clear sinusoidal mod-
ulation in the azimuthal angle distribution in 200 mdash
300 keV (see Figure 16) The polarization angle is also
constrained within 13 uncertainty The Bayes factor for
this interval in 200 mdash 300 keV is found to be sim2 with a
false polarization detection probability by chance lt 1
clearly signifying that the GRB is polarized at the later
part of the emission at higher energies
7 DISCUSSIONS AND CONCLUSIONS
We presented the spectral timing and polarization
analysis of GRB 171010A which has an observed flu-
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Zhang B-B Uhm Z L Connaughton V Briggs M S
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Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 17
Figure 14 Same as Figure 12 but for different energy ranges mdash 100 mdash 200 keV (left) and 200 mdash 300 keV (right) We see asinusoidal modulation in the 200 mdash 300 keV modulation curve
Figure 15 Compton light curve (top) polarization fraction (middle) and angle (bottom) for three different time intervalsduring the prompt emission of GRB 171010A in 100 mdash 200 keV (left) and 200 mdash 300 keV (right)
ence gt 10minus4 ergs cmminus2 We found that the spectrum
integrated over the duration of the burst is peculiar as it
shows a low energy break and can be modeled by either
a BB or another power law Some GRBs have shown
the presence of such a component which was modeled
by a BB with peaks ranging up to 40 keV (Guiriec et al
2011) In a comprehensive joint analysis of X-
rays and higher energies in the prompt emission
a break was found in the XRT-energy window
(Zheng et al 2012 Oganesyan et al 2018 2017)
and also in the GBM energy range (Ravasio et al
2018) To study the detailed evolution of the spectral
parameters we sliced the spectrum into multiple time
bins and found that Band Ep shows a bimodal distri-
bution Inclusion of a low energy component (modeled
as a BB or a separate power-law) shows that the distri-
bution of the peak energy remains gt 100 keV and also
falls in a concentrated region of between 100 minus 200 keV
The mean value of the break energy in the power-law
with two breaks model (E2) is sim 140 keV The power
law index above the break is softer than the index α
obtained from the Band function The mean value of
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
18 Chand et al
Figure 16 Azimuthal angle distribution for the third time interval (28 mdash 70 seconds at 200 mdash 300 keV) We see a clear andhigh modulation signature in the azimuthal distribution The Bayes factor is found to be around 2 with a false polarizationdetection probability by chance less than 1
minusα2 is -145 and we are tempted to identify it with the
synchrotron fast cooling process E2 can therefore be
identified with the minimum energy injected to the elec-
trons and the corresponding frequency is νm On the
other hand minusα1 is 03 harder than the value of spectral
index minus23 allowed below the cooling frequency νc of
synchrotron radiation However absorption frequency
which can be near the GBM lower energy window has
expected index to be +1 thus it is possible that the
cooling frequency falls very near to the absorption fre-
quency In such a case E1 can be either identified as
νc or νa as the ratio νcνa or νaνc will be closer to
1 Now relating to the fast cooling scenario minusα3 can
be set equal to minusp2 minus 1 to get the index of power-
law distribution of electron energies We get p 32
and for the distribution shown by minusα3 allowed values
of p fall in the range 2 to 4 The component at the
low energy end can also be interpreted as being of pho-tospheric origin generated in a region that is optically
thick to the radiation and radiation escaping at a ra-
dius where it becomes transparent We have tested
also the synchrotron model since bkn2pow gives a
possibility that synchrotron model in marginally
fast cooling regime could in principle work The
direct fitting of the prompt emission spectra by
the synchrotron model have been performed in
number of studies (Tavani 1996 Lloyd amp Pet-
rosian 2000 Burgess et al 2014b Zhang et al
2016 2018 Burgess et al 2018) that give the
preference to the slow or moderataly fast cool-
ing regimes of radiation In our analysis the
synchrotron model returns small ratio between
γm and γc and the range of pgstatdof that is
similar to other models and it has same number
of parameters as Band function Our results show
that the spectral data can also be well described by a
Comptonization (grbcomp) model
From the afterglows observed in LAT (gt100 MeV) and
XRT (03 -10 keV) we concluded that the afterglows are
produced in an external shock propagating into the am-
bient medium By assuming the ambient medium to be
homogeneous we estimated the initial Lorentz factor of
the ejecta However the Lorentz factor thus obtained is
for the merged ejecta The sub-MeV emission possibly
arises from multiple internal shocks and a stratification
in the Lorentz factor can not be ruled out From the ob-
served break in the XRT light curve we obtained the jet
opening angle GRB 171010A consists of a jet with ini-
tial beaming angle much narrower than the jet opening
angle
The burst shows high polarization however significant
variation in the polarization fraction (PF) and angle
(PA) can be seen with energy and time Such variations
in PA can arise due to ordered magnetic field or random
magnetic fields produced in shocks and when within the
beaming angle the net magnetic field can be oriented in
any direction independent of the other shells For a high
polarization the coherence length of the magnetic field
(θB) should be larger than or comparable to the beam-
ing angle 1Γ ie θB amp 1Γ In case of a Poynting
flux dominated jet a pulse is produced in each
ICMART event The peak energy and polari-
sation decreases in each ICMART event The
polarisation degree and angle can vary (Zhang
amp Yan 2011 Deng et al 2016) The spectrum
can be a hybrid of blackbody and Band func-
tion We have observed a low energy feature
and the spectrum deviating from Band function
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 19
which was also modelled by a blackbody This
can be contribution from a photosphere (Gao amp
Zhang 2015) The lower polarisation at ener-
gies below 200 keV can be due to multiple events
superimposing and decreasing the net degree of
polarization The change is polarisation angle
with energy also supports this argument There-
fore the spectrum and polarization measurents
are consistent with ICMART model
In the Comptonization model multiple Compton scat-
terings are assumed producing higher energy photons
in the jet The photons below the peak energy in the
grbcomp model are produced by the Comptonization of
the seed blackbody photons during the sub-relativistic
phase This component is therefore expected to be
unpolarized The high energy photons above the peak
energy are mostly generated by further inverse Comp-
ton scattering off the non-thermal relativistic electrons
of the relativistic outflow This can give a polarization
up to 100 when the emission is observed at an an-
gle 1Γ with the beaming axis and unpolarized when
viewed on-axis (Rybicki amp Lightman 1979) As for po-
larization the highest value is expected for emission in
the jet because in this case a photon originating in the
Compton cloud illuminates the jet (or outflow) and un-
dergoes a single up-scattering Single scattering off jet
electrons can result in a degree of polarization up to
100 Change in the polarization fraction and angle can
be possible only if jet is fragmented and we are observ-
ing it at different viewing angles The measured high
polarization below the peak is in contradiction with the
predictions of this model
The photospheric component found in the spectra
suggests that the overall spectral shape may also be
explained by the sub-photospheric dissipation model
(Vurm amp Beloborodov 2016) The polarization expected
in the sub-photospheric dissipation model is low and
tends to decrease at higher energies because the higher
energy photons are produced deep within the photo-
sphere and are reprocessed through multiple Compton
scatterings before finally leaving the system at the pho-
tosphere (Lundman et al 2016) The observed increase
in the polarization with energy is in contradiction with
the predictions of this model
Another interpretation independent of the syn-
chrotron or inverse Compton origin is that the emis-
sion is from fragmented fireballs moving with different
velocity vectors (Lazzati amp Begelman 2009) The frag-
ments moving into the direction of the observer will
have the least polarization If the intrinsic brightness of
all the fragments are the same then this would also be
the brightest fragment The fragments making larger
angle with the line of sight on the other hand will have
higher polarization and lower intensity The polariza-
tion angle can sweep randomly between different pulses
in this setting Another prediction of this geometry is
that the PF and PA should not change within a single
pulse In time integrated analysis we also find a change
in polarization with energy One possible explanation
for this is that given the variability seen in the low en-
ergy light curve (100 - 200 keV) the contribution in
this energy range could be from more fragments than
that in the high energy light curve (200 - 300 keV)
The averaging effect thus results in a relatively lower
polarization fraction (maximum PF up to 100 can be
achieved for the fragments viewed at 1Γ where Γ is
the Lorentz factor of a fragment) and a different posi-
tion angle at lower energies in comparison to those in
the high energy band The change in polarization with
time can be explained by temporally separated internal
shocks produced in the different fragments Therefore
the change in polarization from high to low seen in the
100 - 200 keV energy can be explained by considering
the first pulse produced off-axis and the other brighter
pulses near the axis (line of sight) In the high energy
part an increase in polarization with time is observed as
well as the polarization angle are found to anti-correlate
with the low energy counterpart This suggests that the
high energy emission has increased contribution with
time from energetic off-axis fragments
In the fragmented fireball scenario the jet should be
fragmented into small scale (θfragment lt θbeam) The
Lorentz factor Γ0 was calculated from the LAT high
energy afterglows that were produced in the external
shocks If the internal shocks were produced before the
saturation in Lorentz factor was achieved then we can
have a lower value of Lorentz factor when the internal
shocks occur This will allow a little room to increase
θbeam If the internal shocks are produced at small radii
then the velocity vector within the θbeam for a radially
expanding ejecta will also have more divergence in their
direction
We conclude that the polarization results when used
with spectral and temporal information are highly con-
straining Although we cannot decisively select a single
model we find that models with a decrease in polar-
ization with energy are either less probable or contribu-
tions from multiple underlying shocks in different energy
ranges are needed to explain the apparent modulation
with energy Comptonization model has low polariza-
tion at low energies is contradiction with our observa-
tions However independent of emission mechanisms a
geometric model consisting of multiple fragments can
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
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amp Zhang B 2016 ApJ 816 72
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Nature Astronomy 2 69
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751 90
20 Chand et al
explain the data but demands fragmentation at small
angular scale well within θbeam
ACKNOWLEDGEMENTS
This research has made use of data obtained through
the HEASARC Online Service provided by the NASA-
GSFC in support of NASA High Energy Astrophysics
Programs This publication also uses the data from the
AstroSat mission of the Indian Space Research Organ-
isation (ISRO) archived at the Indian Space Science
Data Centre (ISSDC) CZT-Imager is built by a con-
sortium of Institutes across India including Tata Insti-
tute of Fundamental Research Mumbai Vikram Sarab-
hai Space Centre Thiruvananthapuram ISRO Satellite
Centre Bengaluru Inter University Centre for Astron-
omy and Astrophysics Pune Physical Research Labo-
ratory Ahmedabad Space Application Centre Ahmed-
abad contributions from the vast technical team from
all these institutes are gratefully acknowledged The
polarimetric computations were performed on the HPC
resources at the Physical Research Laboratory (PRL)
We thank Lev Titarchuk for discussions on the grbcomp
model
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Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
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Ravasio M E Oganesyan G Ghirlanda G et al 2018
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22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 21
Table 2 LAT emission (gt 100 MeV) in different time intervals for a fit with a power-law spectrum
Time Index Energy flux Photon flux Test Statistic
(s) ( 10minus9 ergs cmminus2 sminus1) (times10minus7 photons cmminus2 sminus1) (TS)
(0) 0 - 346 minus2 (fixed) lt 144 lt 193 0
(1) 346 - 514 minus235plusmn 033 843plusmn 333 170plusmn 48 39
(2) 514 - 635 minus197plusmn 025 1300plusmn 525 167plusmn 46 85
(3) 635 - 1200 minus195plusmn 025 346plusmn 180 44plusmn 13 62
(4) 1200 - 2150 minus243plusmn 036 123plusmn 048 27plusmn 8 33
(5) 2150 - 6650 minus150plusmn 023 143plusmn 055 90plusmn 14 58
(6) 6650 - 100000 minus2 (fixed) lt 0093 lt 22 9
Table 3 Best fit parameters for power law fits with multiple breaks for the low energy light curve from XRT Power law withtwo breaks is the best fit model
breaks α1 tb1 α2 tb2 α3 tb3 α4
(104 s) (105 s) (105 s)
1 130+007minus008 340+00
minus150 20+00minus00
2 237+032minus017 86+16
minus50 minus095+213minus055 158+157
minus014 185+014minus014
3 237+039minus016 70+00
+30 0+1minus2 18+00
minus04 20+60minus05 80+00
minus60 1+7minus3
Table 4 Spectral fit to the XRT spectra at different time intervals using the power law (PL) model
Time Model nHi αpo CSTATdof
(104 s) PL 1022
Phase 1
(243 - 175) 19+01minus01
Phase 2 027+005minus005
513566
(175 1322) 20+02minus02
Phase 1 PL αpo CSTATdof
(243 258) 145+032minus070
179222
(303 317) 17+01minus01
211246
(359 416) 171+015minus015
204205
(133 175) 19+02minus02
109135
Phase 2
(175 772) 18+02minus02
151188
(85 1322) 14+05minus04
4541
mdash 1999 MNRAS 306 L39
Molinari E Vergani S D Malesani D et al 2007
AampA 469 L13
Narayan R Paczynski B amp Piran T 1992 ApJL 395
L83
Nousek J A Kouveliotou C Grupe D et al 2006 ApJ
642 389
Oganesyan G Nava L Ghirlanda G amp Celotti A
2017 ApJ 846 137
mdash 2018 AampA 616 A138
Omodei N Vianello G amp Ahlgren B 2017 GRB
Coordinates Network Circular Service No 21985
1-2018 (2017) 21985
Page K L Starling R L C Fitzpatrick G et al 2011
MNRAS 416 2078
Poolakkil S amp Meegan C 2017 GRB Coordinates
Network Circular Service No 21992 1-2018 (2017)
21992
Ravasio M E Oganesyan G Ghirlanda G et al 2018
AampA 613 A16
Rees M J amp Meszaros P 1992 MNRAS 258 41P
mdash 1994 ApJL 430 L93
Rybicki G B amp Lightman A P 1979 Radiative
processes in astrophysics
Ryde F 2005 ApJL 625 L95
Sari R amp Piran T 1999 ApJ 520 641
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
22 Chand et al
Table 5 Time-resolved Spectral fitting for different models
Band
Sr no (t1t2) α β Ep (keV) KB pgstatdof
1 -1 7 minus12+01minus01
minus93+194minusinfin 141
+16minus19
0016+0004minus0003
420339
2 7 9 minus110+005minus005
minus88+188minusinfin 222
+28minus23
0029+0004minus0005
284339
3 9 10 minus108+01minus007
minus77+177minusinfin 274
+111minus74
0054+0011minus0009
212339
4 10 12 minus10+01minus01
minus22+02minus05
303+107minus51
0081+0011minus0011
310339
5 12 14 minus090+007minus006
minus23+02minus03
362+72minus52
010+001minus001
311339
6 14 17 minus090+007minus006
minus215+010minus017
329+63minus50
009+001minus001
400339
7 17 18 minus08+01minus01
minus24+02minus04
206+43minus31
018+004minus003
290339
8 18 19 minus08+01minus01
minus240+017minus025
217+27minus23
023+003minus003
210339
9 19 20 minus082+007minus007
minus25+02minus03
241+31minus27
026+003minus003
341339
10 20 24 minus080+003minus003
minus250+008minus001
230+11minus10
033+002minus001
620339
11 24 26 minus100+006minus006
minus26+02minus02
130+10minus9
030+004minus030
443339
12 26 29 minus110+004minus003
minus28+02minus04
196+14minus13
022+001minus001
519339
13 29 30 minus100+007minus006
minus28+03minus16
255+40minus30
022+003minus002
314339
14 30 31 minus100+004minus004
minus94+19494 316
+28minus26
024+002minus001
293339
15 31 32 minus083+005minus005
minus25+02minus03
284+32minus26
035+003minus003
418339
16 32 34 minus082+003minus003
minus25+01minus01
273+17minus15
043+002minus002
506339
17 34 35 minus080+005minus005
minus25+01minus02
264+23minus20
047+004minus003
314339
18 35 36 minus090+005minus005
minus27+02minus05
250+24minus21
040+003minus003
320339
19 36 38 minus080+004minus004
minus26+01minus01
134+7minus6
049+004minus004
480339
20 38 39 minus10+01minus01
minus27+02minus04
101+10minus9
035+007minus005
357339
21 39 41 minus03+03minus03
minus280+005minus006
42+5minus4
259+307minus121
494339
22 41 44 minus125+004minus004
minus3+03minus07
110+7minus6
023+002minus002
612339
23 44 45 minus11+01minus01
minus3+04minusinfin 131
+14minus16
027+005minus004
288339
24 45 46 minus105+005minus005
minus28+03minus11
191+18minus14
032+003minus003
366339
25 46 47 minus10+01minus01
minus25+02minus05
103+15minus12
033+009minus006
356339
26 47 48 minus120+007minus007
minus94+19minusinfin 98
+7minus6
021+003minus003
328339
27 48 50 minus12+02minus01
minus28+04minus12
65+7minus10
017+010minus004
341339
28 50 51 minus11+01minus01
minus29+04minus11
93+11minus11
021+006minus004
291339
29 51 53 minus11+01minus01
minus28+02minus03
99+8minus7
028+004minus003
397339
30 53 55 minus110+005minus004
minus33+06minusinfin 208
+17minus19
021+002minus001
434339
31 55 56 minus100+005minus004
minus41+12minusinfin 248
+22minus21
025+002minus002
329339
32 56 57 minus105+004minus004
minus9+19minusinfin 268
+23minus20
029+002minus002
339339
33 57 58 minus101+004minus004
minus9+19minusinfin 252
+19minus18
036+002minus002
378339
34 58 59 minus100+005minus004
minus29+03minus10
245+25minus21
037+003minus001
390339
35 59 60 minus105+005minus005
minus29+03minus11
233+26minus23
031+003minus002
383339
36 60 61 minus100+006minus006
minus26+02minus06
212+28minus22
037+004minus003
369339
37 61 63 minus100+005minus005
minus25+02minus02
165+13minus12
027+003minus002
421339
38 63 64 minus10+01minus01
minus27+03minus06
141+17minus16
025+005minus004
305339
39 64 65 minus10+01minus01
minus28+03minusinfin 154
+24minus16
029+004minus004
316339
40 65 67 minus100+004minus004
minus28+02minus03
165+11minus10
039+003minus003
551339
41 67 68 minus104+006minus006
minus3+03minus1
137+12minus11
039+005minus004
415339
42 68 69 minus103+005minus005
minus3+03minus07
153+12minus12
049+005minus004
382339
43 69 70 minus10+02minus01
minus230+013minus015
87+13minus16
043+023minus009
389339
44 70 71 minus108+006minus006
minus280+025minus064
140+15minus12
034+004minus004
379339
45 71 72 minus100+004minus002
minus9+19minusinfin 158
+8minus4
046+003minus003
363339
46 72 73 minus102+009minus008
minus28+03minus04
93+8minus8
039+008minus006
316339
47 73 74 minus09+08minus02
minus24+02minus02
56+12minus19
045+179minus018
315339
48 74 76 minus110+007minus006
minus28+02minus03
89+6minus6
0331+005minus004
506339
49 76 77 minus11+01minus01
minus29+04minus07
84+9minus8
027+007minus005
313339
50 77 78 minus03+05minus09
minus21+01minus08
47+57minus8
168+371minus168
318339
51 78 82 minus12+01minus01
minus26+02minus02
75+6minus7
015+003minus002
500339
52 82 84 minus11+01minus01
minus24+02minus02
139+15minus14
020+003minus002
441339
53 84 85 minus11+02minus01
minus270+035minusinfin 109
+28minus17
011+004minus003
252339
54 85 90 minus12+02minus01
minus26+03minus01
76+7minus14
013+008minus002
560339
55 90 101 minus12+01minus01
minus24+02minus03
83+9minus10
006+002minus001
529339
56 101 113 minus130+008minus007
minus30+04minus10
86+8minus8
004+001minus001
506339
57 113 136 minus13+01minus01
minus3+05minus08
66+4minus6
0036+0008minus0004
676339
58 136 137 minus13+01minus01
minus9+19minusinfin 83
+13minus10
008+003minus002
266339
59 137 150 minus13+01minus01
minus3+04minusinfin 66
+5minus5
004+001minus001
491339
60 150 171 minus11+14minus03
minus23+02minus02
33+8minus12
004+026minus002
382339
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β K pgstatdof
1 -1 7 [minus30] 123+02minus11
16+06minus06
256+47minus122
7+infinminus4
00001+0002minus000004
408337
2 7 9 [minus30] 127+18minus20
14+01minus01
142+59minus28
24+06minus03
00002+00002minus000007
275338
3 9 10 09+07minus05
17+infinminus17
13+01minus01
194+73minus51
25+07minus04
5+29minus5
215338
4 10 12 minus05+05minusinfin 170
+12minus15
125+005minus004
170+41minus23
21+01minus01
014+002minus001
287338
5 12 14 02+06minus07
18+5minus4
120+004minus005
212+52minus27
22+01minus01
09+26minus09
315337
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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Scargle J D Norris J P Jackson B amp Chiang J 2013
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Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
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Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
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2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
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Vianello G Gill R Granot J et al 2017 ArXiv
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859 160
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Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 23
Table 5 Time-resolved Spectral fitting (continued)
Broken power-law
Sr no (t1t2) α1 E1 (keV) α2 E2 (keV) β Kb pgstatdof
6 14 17 minus1+1minus1
16+3minus2
120+005minus004
185+50minus22
21+01minus01
0023+0296minus0023
373337
7 17 18 minus08+0808 15
+2minus2
110+007minus006
124+23minus13
22+01minus01
011+003minus002
288338
8 18 19 04+03minus04
19+infinminus19
100+006minus006
1380+223minus154
22+01minus01
298+478minus298
218338
9 19 20 minus02+08minus09
17+4minus4
110+005minus005
146+14minus12
23+01minus01
067+473minus067
337337
10 20 24 minus02+04minus07
17+2minus2
110+002minus002
158+8minus8
230+005minus005
080+143minus066
611337
11 24 26 minus08+12minus08
15+5minus2
140+006minus004
118+10minus9
25+01minus01
025+207minus025
386337
12 26 29 02+03minus05
18+2minus1
150+002minus002
352+24minus26
53+08minus06
0013+0001minus0001
571337
13 29 30 minus13+12minus08
155+25minus15
130+004minus004
205+30minus28
26+02minus02
0044+0490minus0044
283337
14 30 31 minus01+05minus06
15+infinminus15
120+003minus003
177+16minus14
24+01minus01
116+350minus116
298338
15 31 32 minus06+04minus05
167+infinminus167
110+003minus003
1860+204minus173
23+01minus01
035+070minus035
408338
16 32 34 minus02+04minus08
180+27minus23
110+003minus003
1750+13minus11
230+006minus005
109+217minus109
485337
17 34 35 006+040minus060
19+4minus4
110+004minus004
174+15minus13
23+01minus01
215+408minus215
317337
18 35 36 01+04minus07
18+3minus3
110+004minus003
159+14minus12
24+01minus01
231+452minus231
319337
19 36 38 minus03+04minus06
17+14minus15
130+003minus003
116+7minus6
250+007minus007
110+169minus110
386337
20 38 39 minus03+05minus10
17+2minus2
160+005minus005
114+16minus13
27+02minus02
094+266minus094
294337
21 39 41 03+03minus03
190+15minus14
180+004minus005
126+22minus22
3+03minus03
524+523minus310
391337
22 41 44 minus06+02minus03
15+infinminus15
160+002minus002
133+11minus10
280+014minus014
051+044minus029
443338
23 44 45 [minus25] 123+06minus07
140+004minus004
108+13minus11
25+02minus01
0005+0001minus0001
271338
24 45 46 [minus20] 144+06minus06
140+003minus003
169+16minus21
26+02minus02
0013+0002minus0001
292338
25 46 47 [minus30] 130+05minus05
150+004minus005
110+12minus17
25+02minus02
0001200002minus00002 313338
26 47 48 [minus30] 130+06minus06
160+004minus005
121+17minus14
30+03minus03
000128+00003minus00002
290338
27 48 50 [minus30] 126+04minus04
180+004minus005
104+13minus23
30+04minus04
000114+00002minus00002
288338
28 50 51 [minus30] 133+07minus07
160+006minus006
109+20minus17
28+04minus03
000085+00002minus00002
255338
29 51 53 minus08+08minus10
150+16minus14
160+004minus004
113+15minus13
27+02minus02
024+153minus024
335337
30 53 55 [minus30] 13+04minus04
140+003minus003
157+17minus14
25+01minus01
00011+00002minus00001
370338
31 55 56 minus02+06minus07
17+3minus3
130+004minus004
200+31minus24
26+02minus02
088+329minus088
309337
32 56 57 minus12+15minus09
14+4minus1
130+004minus003
177+19minus15
25+01minus01
009+096minus009
330337
33 57 58 minus06+1minus08
150+31minus23
130+003minus003
169+15minus13
250+014minus012
056+212minus056
359337
34 58 59 minus06+09minus05
150+30minus23
130+003minus003
168+14minus12
24+01minus01
057+299minus057
366337
35 59 60 04+03minus04
210+34minus28
140+004minus004
211+36minus25
26+02minus01
593+667minus402
364337
36 60 61 02+04minus05
190+30minus23
140+004minus003
166+14minus13
24+01minus01
340+585minus258
330337
37 61 63 [minus3] 130+05minus05
130+003minus003
120+9minus9
23+01minus01
00012+00002minus00002
375338
38 63 64 minus14+14minusinfin 14
+1minus1
130+005minus005
120+15minus13
250+016minus015
004+0007minus0005
283338
39 64 65 040+035minus040
21+5minus3
150+006minus005
164+23minus26
27+02minus02
451+711minus304
289337
40 65 67 minus08+07minus10
153+19minus16
100+003minus003
132+10minus9
250+008minus008
032+168minus032
461337
41 67 68 minus05+07minus1
160+21minus16
140+004minus004
130+14minus14
26+02minus02
081+382minus081
366337
42 68 69 02+04minus06
18+3minus4
14+005minus01
146+18minus30
26+02minus03
5+10minus5
340337
43 69 70 minus007+04minus05
170+18minus17
160+005minus005
109+18minus16
24+01minus01
215+462minus215
334337
44 70 71 005+030minus050
18+2minus2
15+004minus004
154+20minus18
27+02minus02
262+364minus2624
301337
45 71 72 minus02+05minus05
17+18minus16
140+003minus003
149+12minus10
28+02minus01
159+397minus159
307337
46 72 73 03+03minus05
182+22minus20
160+005minus005
105+10minus9
270+014minus020
557+805minus557
275337
47 73 74 04+03minus09
18+2minus5
18+01minus02
110+31minus44
27+03minus04
560812minus560 278337
48 74 76 minus01+04minus08
16+15minus17
16+004minus005
108+12minus15
27+02minus02
186362minus186 410337
49 76 77 04+04minus05
19+3minus2
170+006minus005
129+15minus17
30+04minus03
452+812minus452
285337
50 77 78 minus1+1minus1
150+33minus16
170+006minus006
136+21minus34
30+04minus03
018+352minus018
271337
51 78 82 03+03minus05
173+15minus17
180+004minus004
108+12minus10
27+02minus02
291+358minus215
381337
52 82 84 minus13+09minus09
150+15minus11
150+004minus004
128+20minus15
24+02minus01
006+057minus006
352337
53 84 85 03+06minus08
170+44minus53
16+01minus01
119+23minus24
26+04minus03
215+485minus215
238337
54 85 90 minus02+06minus08
16+2minus2
180+004minus005
118+15minus21
28+02minus02
071227minus071 462337
55 90 101 [minus2] 127+04minus04
160+003minus005
101+13minus23
25+02minus03
000456000054minus000046 470338
56 101 113 [minus3] 128+04minus04
170+003minus003
122+14minus12
29+03minus03
000027+000004minus000003
403338
57 113 136 [minus30] 1220+004minus030
18+003minus006
97+15minus15
29+04minus03
00003+0000005minus000003
556337
58 136 137 [minus30] 124+09minus10
180+007minus006
181+51minus68
51+infinminus22
00008+00003minus00002
256338
59 137 150 [minus30] 116+01minus04
170+004minus004
94+12minus10
29+04minus02
00004+000001minus000006
449337
60 150 171 04+08minus08
140+4minus15
20+01minus01
95+39minus62
29+08minus06
093+578minus093
372337
b photons keVminus1 cmminus2 sminus1 at 1 keV
24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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24 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
BB+Band
Sr no (t1t2) α β Ep (keV) KB kTBB (keV) KBB pgstatdof
1 -1 7 minus09+05minus03
minus94+19minusinfin 153
+34minus23
002+001minus001
65+24minus16
050+039minus034
414337
2 7 9 001+180minus090
minus24+03minusinfin 149
+68minus34
008+036minus005
55+13minus11
136+078minus081
276337
3 9 10 minus11+02minus02
minus9+19minusinfin 299
+191minus41
005+001minus001
13+infinminus8
073+200minus073
212337
4 10 12 minus04+04minus04
minus21+01minus02
215+81minus34
012+006minus004
70+15minus10
255+078minus103
296337
5 12 14 minus08+02minus03
minus22+01minusinfin 331
+383minus59
010+002minus004
72+infinminus31
079+105minus079
309337
6 14 17 minus05+04minus02
minus21+01minus01
260+66minus54
011+005minus002
80+15minus11
209+106minus088
383337
7 17 18 minus05+05minus02
minus23+02minus03
185+51minus34
022+017minus004
7+7minus2
213+220minus190
287337
8 18 19 minus07+03minus04
minus24+02minusinfin 219
+219minus34
023+008minus012
10+infinminus10
120+224minus120
209337
9 19 20 minus06+05minus02
minus24+02minus03
218+42minus41
031+017minus006
70+30minus15
316+299minus221
335337
10 20 24 minus05+01minus01
minus24+01minus01
212+14minus12
039+004minus004
73+08minus06
426+119minus114
579337
11 24 26 minus01+04minus03
minus25+01minus01
122+10minus9
063+041minus019
60+04minus04
779+214minus194
390337
12 26 29 minus08+01minus01
minus100+00minusinfin 196
+8minus7
025+002minus002
60+05minus05
455+099minus094
458337
13 29 30 minus05+01minus02
minus26+02minus03
213+33minus21
030+011minus006
70+09minus08
563+214minus208
293337
14 30 31 minus07+02minus02
minus30+02minus06
256+59minus31
029+006minus004
57+15minus12
274+203minus137
289337
15 31 32 minus06+02minus02
minus24+01minus02
254+38minus30
040+008minus006
74+23minus15
414+257minus236
409337
16 32 34 minus05+01minus01
minus24+01minus01
241+20minus18
052+007minus005
80+07minus06
767+213minus200
460337
17 34 35 minus05+02minus01
minus24+01minus01
241+27minus26
054+011minus007
77+16minus12
562+314minus278
302337
18 35 36 minus06+03minus02
minus26+02minus03
224+32minus30
046+013minus007
67+19minus12
425+303minus256
313337
19 36 38 01+04minus03
minus25+01minus01
122+8minus7
123+070minus036
60+03minus03
1135+250minus235
400337
20 38 39 03+1minus06
minus27+02minus02
1030+105minus95
121+303minus061
59+04minus04
1189+333minus313
305337
21 39 41 minus04+05minus03
minus28+02minus03
99+8minus9
050045minus016 60+04minus03
1120+222minus193
399337
22 41 44 minus04+03minus02
minus28+02minus02
116+7minus7
049+020minus011
55+02minus02
1036+160minus148
456337
23 44 45 minus05+05minus04
minus26+02minus03
116+17minus12
052+049minus019
50+08minus06
601+302minus289
276337
24 45 46 minus04+02minus01
minus25+01minus02
167+16minus9
053+006minus010
65+04minus05
1077+156minus148
317337
25 46 47 minus02+08minus05
minus25+02minus03
107+16minus13
070+117minus031
60+07minus05
929+336minus290
320337
26 47 48 minus03+07minus05
minus31+04minusinfin 108
+14minus10
045+051minus019
57+06minus05
826+263minus273
293337
27 48 50 minus03+11minus05
minus28+03minus06
81+8minus6
042+175minus021
495+040minus034
587+205minus180
303337
28 50 51 01+13minus07
minus28+03minus06
99+13minus12
067+282minus038
55+05minus05
690+259minus259
268337
29 51 53 minus04+03minus03
minus27+02minus02
100+8minus7
058+029minus017
50+infinminus01
653+143minus177
354337
30 53 55 minus07+02minus02
minus27+02minus04
177+21minus17
029+007minus005
60+06minus05
509+156minus155
402337
31 55 56 minus07+02minus01
minus4+1minusinfin 241
+23minus26
028+005minus003
7+1minus1
548+213minus198
307337
32 56 57 minus09+01minus01
minus9+19minusinfin 267
+23minus20
0305+0065minus0022
75+14minus12
487+221minus212
325337
33 57 58 minus08+02minus01
minus31+05minusinfin 234
+25minus25
041+007minus005
7+1minus1
684+257minus249
356337
34 58 59 minus07+02minus02
minus26+02minus04
219+29minus23
044+009minus006
7+1minus1
737+283minus267
367337
35 59 60 minus08+02minus01
minus28+03minus06
225+31minus26
034+006minus004
8+1minus1
639+238minus224
359337
36 60 61 minus06+03minus02
minus25+014minus03
190+35minus20
048+014minus010
70+10minus07
953+305minus275
330337
37 61 63 minus05+04minus03
minus240+012minus015
143+17minus15
046+024minus012
57+05minus04
583+204minus188
389337
38 63 64 minus04+06minus04
minus25+02minus02
130+22minus18
041+040minus014
60+13minus08
468+249minus228
293337
39 64 65 minus080+040minus015
minus34+0834 182
+25minus34
028+015minus005
84+14minus15
731+235minus224
285337
40 65 67 minus03+02minus02
minus26+01minus01
146+10minus9
069+019minus013
63+03minus02
1053+200minus198
464337
41 67 68 minus04+04minus03
minus27+02minus03
132+13minus11
066+034minus017
60+06minus05
1057+319minus293
373337
42 68 69 minus06+03minus02
minus27+02minus04
147+15minus13
069+024minus014
64+07minus05
1130+322minus300
336337
43 69 70 minus015+11minus05
minus24+01minus02
97+18minus15
096+277minus051
60+07minus04
1153+410minus346
345337
44 70 71 minus05+03minus02
minus27+02minus03
141+14minus13
053+023minus012
60+05minus05
1114+270minus253
318337
45 71 72 minus05+02minus02
minus32+03minus10
153+10minus10
065+017minus011
60+06minus05
1067+290minus284
317337
46 72 73 01+11minus06
minus27+02minus03
97+10minus8
125344minus067 60+04minus04
1190+422minus381
276337
47 73 74 01+infinminus06
minus26+02minus02
81+10minus9
104+029minus003
52+04minus03
973+128minus047
275337
48 74 76 01+08minus04
minus27+02minus02
95+7minus8
114+226minus049
55+03minus03
1156+280minus238
413337
49 76 77 minus05+05minus04
minus3+03minus07
98+11minus9
040+036minus015
60+09minus06
666+254minus230
290337
50 77 78 minus05+06minus04
minus28+03minus06
111+15minus13
038+042minus014
62+07minus05
902+262minus252
275337
51 78 82 00+07minus04
minus27+02minus02
91+6minus6
049+066minus021
50+02minus02
657+123minus120
386337
52 82 84 minus03+05minus03
minus2+01minus02
131+15minus15
038028minus011 60+05minus04
661+167minus155
380337
53 84 85 04+40minus10
minus26+03minus04
104+17minus19
054+6034minus036
55+08minus06
513+204minus206
235337
54 85 90 minus03+1minus04
minus26+02minus02
91+8minus11
031+043minus012
53+03minus03
464+139minus097
463337
55 90 101 minus02+45minus04
minus25+02minus02
88+101minus20
017+7502minus008
5+03minus03
202+119minus053
477337
56 101 113 minus03+05minus04
minus3+03minus05
100+10minus8
009+008minus003
5+03minus03
169+036minus036
441337
57 113 136 025minus025minus090
minus26+02minus06
72+11minus11
027+4062minus019
45+02minus02
165+056minus046
610337
58 136 137 minus08+06minus04
minus93+1993 103
+18minus15
011+0102minus004
50+08minus07
285+171minus170
257337
59 137 150 minus05+07minus04
minus3+03minus06
79+6minus6
010+015minus004
40+03minus03
140+049minus047
463337
60 150 171 minus11+11minus04
minus28+05minusinfin 63
+16minus24
002+036minus001
4+1minus1
057+084minus030
374337
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
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859 160
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Nature Astronomy 2 69
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751 90
Variable prompt emission polarization in GRB 171010A 25
Table 5 Time-resolved Spectral fitting (continued)
grbcomp
Sr no (t1t2) kTs (keV) kTe (keV) τ δ αb Rph (1010) cm pgstatdof
1 -1 7 [53] 90+4minus14
[32] 150 plusmn minus005 30+infinminus24
87+02minus03
412339
2 7 9 [41] 77+20minus32
40+15minus09
180 plusmn 007 26+infinminus13
17+1minus1
281338
3 9 10 [45] 78+40minus32
4+1minus1
170 plusmn 006 18+16minus07
20+1minus1
213338
4 10 12 77+15minus18
117+90minus62
30+21minus08
120 plusmn 003 14+06minus03
10+6minus2
287337
5 12 14 65+17minus26
86+30minus22
4+1minus1
160 plusmn 005 1302minus02 14+17minus4
305337
6 14 17 81+15minus17
91+45minus31
36+15minus08
150 plusmn 005 12+02minus01
9+4minus2
371337
7 17 18 [7] 57+32minus18
50+27minus14
240 plusmn 013 14+04minus02
147+03minus03
283338
8 18 19 [6] 58+16minus12
5+1minus1
236 plusmn 012 14+03minus02
216+04minus04
207338
9 19 20 74+17minus23
62+19minus16
45+20minus10
220 plusmn 010 15+03minus02
17+16minus4
329337
10 20 24 73+07minus08
63+7minus6
48+05minus04
22 plusmn 01 15+01minus01
19+4minus2
551337
11 24 26 76+07minus07
355+115minus93
7+15minus2
38 plusmn 03 16+03minus02
17+3minus2
386337
12 26 29 68+05minus05
530+98minus78
50+10minus07
26 plusmn 014 170+02minus015
20+3minus2
462337
13 29 30 77+11minus12
69+22minus17
45+15minus09
20 plusmn 01 17+04minus02
16+6minus3
286337
14 30 31 63+11minus15
672+137minus101
49+09minus07
20 plusmn 01 16+03minus02
23+16minus5
285337
15 31 32 71+13minus15
743+153minus126
45+08minus06
183 plusmn 007 15+02minus01
21+11minus4
397337
16 32 34 83+08minus09
71+10minus9
46+06minus05
19 plusmn 01 15+01minus01
19+4minus2
437337
17 34 35 76+13minus16
68+12minus11
48+10minus06
2 plusmn 01 15+02minus01
22+11minus4
291337
18 35 36 70+12minus15
64+12minus11
50+10minus07
2 plusmn 01 16+02minus02
24+14minus5
304337
19 36 38 80+05minus06
300+64minus52
126+infinminus53
45 plusmn 05 16+01minus01
18+2minus8
395337
20 38 39 75+05minus05
285+26minus25
[10] 47 plusmn 05 18+02minus02
18+2minus2
302338
21 39 41 70+05minus05
50+25minus20
38+25minus09
27 plusmn 02 24+17minus06
20+3minus2
388337
22 41 44 70+04minus04
40+10minus84
58+27minus12
34 plusmn 03 20+03minus03
21+2minus2
448337
23 44 45 60+09minus13
42+18minus15
50+51minus13
32 plusmn 02 18+06minus03
25+14minus5
271337
24 45 46 78+08minus08
54+16minus13
50+23minus11
25 plusmn 01 17+04minus02
19+4minus3
310337
25 46 47 7+1minus1
47+32minus23
44+116minus14
29 plusmn 02 19+11minus04
20+7minus3
314337
26 47 48 7+1minus1
47+25minus18
50+62minus14
29 plusmn 02 28+infinminus09
19+6minus3
290337
27 48 50 61+07minus08
33+24minus17
5+infinminus2
41 plusmn 04 22+21minus06
20+6minus3
302337
28 50 51 7+1minus1
27+24minus8
11+infinminus7
51 plusmn 06 20+13minus04
16+6minus2
267337
29 51 53 68+06minus07
43+16minus13
48+3minus11
31 plusmn 02 22+08minus04
20+5minus3
335337
30 53 55 64+06minus07
64+14minus12
43+09minus06
21 plusmn 01 19+04minus03
23+5minus3
387337
31 55 56 72+11minus15
85+20minus18
39+08minus05
160 plusmn 006 23+12minus05
19+8minus3
301337
32 56 57 67+11minus13
83+20minus17
38+07minus05
160 plusmn 006 20+06minus03
24+11minus4
317337
33 57 58 69+10minus13
78+16minus14
40+07minus05
175 plusmn 007 21+06minus04
25+11minus4
349337
34 58 59 70+10minus11
72+15minus13
42+08minus06
19 plusmn 01 18+03minus02
24+9minus4
359337
35 59 60 69+10minus12
86+20minus18
35+06minus05
160 plusmn 006 20+05minus03
23+101minus4
345337
36 60 61 75+10minus12
81+25minus21
35+10minus06
167 plusmn 006 18+05minus03
21+7minus3
315337
37 61 63 67+07minus07
44+12minus10
56+25minus11
31 plusmn 02 15+02minus02
21+5minus3
378337
38 63 64 66+11minus14
45+20minus16
5+5minus1
30 plusmn 02 17+06minus03
19+11minus4
288337
39 64 65 73+12minus18
827+30minus252
33+1minus06
160 plusmn 006 25+25minus07
19+7minus4
277337
40 65 67 75+05minus06
47+10minus9
55+18minus1
29 plusmn 02 17+02minus02
21+3minus2
447337
41 67 68 71+07minus08
49+16minus13
5+24minus11
28 plusmn 02 20+06minus03
23+6minus3
366337
42 68 69 70+07minus08
57+16minus14
43+13minus07
24 plusmn 01 20+06minus03
26+6minus3
323337
43 69 70 66+07minus1
75+42minus47
29+43minus07
18 plusmn 01 20+13minus06
24+8minus3
335337
44 70 71 74+07minus08
56+21minus16
42+20minus09
24 plusmn 01 20+07minus03
21+4minus3
308337
45 71 72 72+07minus07
56+10minus95
48+1minus07
24 plusmn 01 24+07minus04
24+5minus3
306337
46 72 73 74+07minus09
26+18minus62
118minus12minus7
52 plusmn 06 19+05minus02
20+5minus2
274337
47 73 74 70+05minus06
230+33minus32
[10] 60 plusmn 08 17+03minus02
20+3minus2
275338
48 74 76 72+05minus05
250+117minus64
128+infinminus72
55 plusmn 06 18+02minus02
minus20+3minus2
406337
49 76 77 67+09minus13
45+28minus21
43+64minus125
30 plusmn 02 24+37minus07
19+10minus3
284337
50 77 78 72+09minus1
52+34minus27
40+84minus12
26 plusmn 02 23+4minus07
18+5minus3
270337
51 78 82 [7] 24+82minus55
11+infinminus5
57 plusmn 07 2+02minus02
153+02minus02
384338
52 82 84 74+07minus07
384+171minus123
6+86minus19
35 plusmn 03 14+03minus02
16+3minus2
375337
53 84 85 7+1minus1
38+6minus6
[6] 36 plusmn 03 20+08minus05
14+4minus2
237338
54 85 90 66+05minus05
32+19minus15
58+infinminus2
42 plusmn 04 20+06minus03
15+2minus2
462337
55 90 101 61+04minus04
30+34minus34
[6] 45 plusmn 04 17+03minus02
12+2minus1
473338
56 101 113 65+06minus06
39+20minus15
50+83minus16
35 plusmn 03 22+15minus05
9+2minus1
437337
57 113 136 58+05minus05
25+17minus10
78+infinminus34
20 plusmn 01 19+10minus04
11+2minus1
603337
58 136 137 58+1minus2
67+26minus26
35+19minus08
20 plusmn 01 30+infinminus27
17+18minus4
256337
59 137 150 56+06minus07
28+16minus12
66+160minus23
48 plusmn 05 22+14minus05
12+4minus2
462337
60 150 171 45+09minus17
61+146minus50
30+21minus13
22 plusmn 01 34+infinminus20
13+19minus3
372337
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
26 Chand et al
Table 5 Time-resolved Spectral fitting (continued)
Synchrotron model
Sr no (t1t2) γmγc Ec (keV) p pgstatdof
1 -1 7 36+05minus14
182+34minus57
gt 304 420339
2 7 9 37+35minus21
296+220minus121
gt 233 286339
3 9 10 35+08minus21
412+150minus132
gt 243 214339
4 10 12 50+14minus16
452+87minus65
gt 298 296339
5 12 14 41+07minus13
698+124minus89
gt 318 302339
6 14 17 48+13minus18
605+113minus74
gt 269 384339
7 17 18 26+09minus21
624+1258minus113
gt 286 285339
8 18 19 18+08minus08
819+1507minus192
393+089minus087
207339
9 19 20 19+08minus09
848+1463minus179
gt 341 334339
10 20 24 16+01minus01
895+1337minus105
388+054minus037
602339
11 24 26 23+03minus07
354+73minus23
gt 328 434339
12 26 29 33+01minus03
328+09minus26
gt 424 558339
13 29 30 31+06minus07
517+107minus69
gt 381 311339
14 30 31 23+05minus04
776+119minus121
gt 413 298339
15 31 32 23+04minus05
909+205minus64
gt 409 406339
16 32 34 18+03minus01
994+192minus104
gt 362 485339
17 34 35 15+06minus02
1137+2009minus199
gt 337 304339
18 35 36 21+02minus08
814+858minus53
gt 433 314339
19 36 38 17+00minus07
629+12minus126
360+034minus027
478339
20 38 39 23+05minus07
261+60minus43
gt 356 347339
21 39 41 27+01minus06
155+25minus14
gt 367 470339
22 41 44 35+02minus03
149+18minus09
gt 455 572339
23 44 45 24+01minus06
302+65minus33
gt 377 285339
24 45 46 29+01minus04
376+24minus52
gt 389 364339
25 46 47 28+05minus08
229+49minus34
gt 341 339339
26 47 48 25+01minus05
197+14minus34
gt 399 321339
27 48 50 27+01minus08
132+32minus17
gt 345 326339
28 50 51 20+02minus06
263+60minus65
gt 358 287339
29 51 53 25+01minus05
230+39minus12
gt 399 378339
30 53 55 35+04minus05
301+40minus28
gt 428 446339
31 55 56 26+01minus04
533+62minus85
gt 404 345339
32 56 57 30+05minus05
473+73minus53
gt 420 351339
33 57 58 28+04minus05
508+78minus54
gt 410 392339
34 58 59 28+04minus04
507+64minus57
gt 405 397339
35 59 60 33+06minus04
405+48minus48
gt 413 374339
36 60 61 32+04minus05
407+49minus41
gt 405 346339
37 61 63 29+01minus06
360+42minus11
gt 366 414339
38 63 64 22+03minus15
395+698minus66
gt 302 302339
39 64 65 27+05minus06
340+64minus47
gt 390 300339
40 65 67 25+05minus03
400+18minus31
gt 439 531339
41 67 68 25+01minus04
314+40minus43
gt 398 406339
42 68 69 27+03minus04
333+45minus34
gt 401 367339
43 69 70 29+01minus08
195+41minus22
gt 342 361339
44 70 71 31+04minus05
254+40minus30
gt 392 358339
45 71 72 20+01minus03
447+63minus56
gt 454 372339
46 72 73 22+04minus06
250+53minus37
gt 377 305339
47 73 74 25+07minus09
149+58minus33
gt 297 303339
48 74 76 25+01minus04
205+29minus16
gt 396 481339
49 76 77 23+05minus08
214+62minus41
gt 340 303339
50 77 78 28+01minus08
177+42minus23
gt 336 300339
51 78 82 29+06minus07
136+25minus17
gt 331 465339
52 82 84 32+10minus10
240+44minus34
gt 268 427339
53 84 85 31+04minus13
192+82minus38
gt 298 250339
54 85 90 28+01minus06
150+25minus13
gt 360 524339
55 90 101 32+02minus11
142+32minus13
gt 295 511339
56 101 113 33+02minus07
128+23minus12
gt 352 485339
57 113 136 29+01minus06
113+19minus17
gt 372 654339
58 136 137 30+12minus10
130+18minus46
gt 339 265339
59 137 150 30+08minus06
112+24minus12
gt 370 485339
60 150 171 21+16minus17
76+155minus33
gt 256 378339
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90
Variable prompt emission polarization in GRB 171010A 27
Sari R Piran T amp Narayan R 1998 ApJL 497 L17
Scargle J D Norris J P Jackson B amp Chiang J 2013
ApJ 764 167
Tavani M 1996 ApJ 466 768
Tierney D McBreen S Preece R D et al 2013 AampA
550 A102
Titarchuk L Farinelli R Frontera F amp Amati L 2012
ApJ 752 116
Vadawale S V Chattopadhyay T Rao A R et al
2015 Astronomy amp Astrophysics 578 73
Vadawale S V Chattopadhyay T Mithun N P S et al
2017 Nature Astronomy doi101038s41550-017-0293-z
Vianello G Gill R Granot J et al 2017 ArXiv
e-prints arXiv170601481
Vurm I amp Beloborodov A M 2016 ApJ 831 175
Wang X-G Zhang B Liang E-W et al 2018 ApJ
859 160
Wang Y-Z Wang H Zhang S et al 2017 ApJ 836 81
Willingale R Starling R L C Beardmore A P Tanvir
N R amp OrsquoBrien P T 2013 MNRAS 431 394
Woosley S E amp Bloom J S 2006 ARAampA 44 507
Zhang B Fan Y Z Dyks J et al 2006 ApJ 642 354
Zhang B amp Yan H 2011 ApJ 726 90
Zhang B-B Uhm Z L Connaughton V Briggs M S
amp Zhang B 2016 ApJ 816 72
Zhang B-B Zhang B Castro-Tirado A J et al 2018
Nature Astronomy 2 69
Zheng W Shen R F Sakamoto T et al 2012 ApJ
751 90