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Early Fermi LAT observations of the Vela pulsar. Massimiliano Razzano on behalf of the Fermi LAT Collaboration. INFN-Pisa [email protected]. ID of Vela pulsar. Radio pulsation discovered in 1968 in the Vela SNR, bright pulsar: S 1.4Ghz ~1.5 Jy - PowerPoint PPT Presentation
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M.Razzano - 44th Rencontres de Moriond
Early Fermi LAT observations of the
Vela pulsar
Massimiliano Razzano on behalf of the Fermi LAT Collaboration
ID of Vela pulsarID of Vela pulsar Radio pulsation discovered in 1968 in the Vela SNR, bright pulsar: S1.4Ghz~1.5 Jy
Located RA=08:35:20.61,dec=-45:10:34.87 (near the Galactic plane @b~-2.8˚)
D~287+19-17 pc (VLBI parallax in 2003)
P:~89 ms; Pdot ~3x10-13 s/s
Young pulsar c~11 kyr
Energetic Edot~7x1036 erg/s
Bsurf ~3.4x1012 G
7 high confidence gamma-ray pulsarsLow confidence gamma-ray pulsars(D. Thompson, 2003)
A huge gamma-ray telescope !
020000400006000080000
100000120000140000160000180000200000
Events
SAS-2 COS-B EGRET AGILE FermiLAT
LATexpected(~1 yr)
Collected photons from Vela at different g-ray telescopes
Thompson et al. 1975
Kanbach et al. 1980Kanbach et al. 1994Pellizzoni et al. 2008
Abdo et. al 2008
A huge teamwork !
•Large collaborative effort of
scientific/instrumental analysis!
•See Abdo et al. 2009 ApJ in press,
arXiv:0812.2960
Point Spread FunctionPoint Spread Function
• Flight data on Vela used for testing the pre-launch expectations• The PSF is very sharp at high energy
Excellent agreementwith pre-launchexpectations below few GeV
Stefano Germani’s talk about on-orbit performance
verifications & monitoring
First First Fermi Fermi Vela light curveVela light curve
100 MeV < E < 10 GeV
~50000 photons !
Remarkablysharp peaks;features to ~0.3 ms
Turns almostcompletely offbetween thedouble pulses
Light curve evolution with energyLight curve evolution with energy
Large LAT energy window puts Vela pulsar in multiwavelength context !
Vela in RadioVela in Radio
• Coherent radio emission– Parkes 64m telescope– RMS residuals 90s
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Synchrotron optical/uv– HST STIS/MAMA – 4.1-6.5 eV(Romani et al., ApJ 2005)
Vela in UVVela in UV
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Thermal soft X-rays
–XMM PN
Soft X-raysSoft X-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Synchrotron hard X-rays
–RXTE PCA(Harding et al., ApJ 2002)
Hard X-raysHard X-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second
– Known from EGRET
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second
– Known from EGRET
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second– Known from EGRET
– 3rd Peak, which shift in energy
– New result !
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second– Known from EGRET
– 3rd Peak, which shift in energy
– New result !
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
Vela in Vela in gg-rays-rays• Curvature g-rays
– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second– Known from EGRET
– 3rd Peak, which shift in energy
– New result !
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second
– Known from EGRET
– Trailing peak survives (known from EGRET)
Vela in Vela in gg-rays-rays
Phase-averaged spectrumPhase-averaged spectrum
Consistent with b=1 (simple exponential)
b=2 (super-exponential) rejected at 16.5s
No evidence for magnetic pair attenuation:Near-surface emission ruled out
N(E) N0E e (E /Ec )b
1.51 0.050.04
Ec 2.9 0.1 GeV
The Vela pulsar movie
E<300MeV (red)300MeV<E<1GeV(Green)E>1GeV (blue)
Summary of key resultsSummary of key results• Vela pulsar
– Phase-averaged spectrum• Simple exponential cutoff Ec = 2.9 ± 0.1 GeV• Inconsistent with magnetic pair attenuation, thus favoring outer
magnetosphere emission models– Energy-dependent pulse profile
• First peak is softer than second peak (confirming EGRET)• Sharpest features to ~0.3 ms.• Peak in bridge region (phase ~ 0.3) shifts to later phase with increasing g-ray
energy– Upper limit on unpulsed emission (>100 MeV)
• 1.8x10-7 ph/cm2/s 95% C.L. upper limit on unpulsed emission, e.g. PWN (Talk of Marie-Helene Grondin)
• Stringent limits or measurement will be available with more livetime– See Abdo et al. 2009 ApJ in press, arXiv:0812.2960
• Contact authors R. Romani and M. Razzano• Fermi LAT & Vela
– Working as designed, performance as expected• e.g. Vela results demonstrate timing and angular resolution below few GeV
(Talk of Stefano Germani)
