ASTROSAT Scienceand synergy with NuSTAR
Dipankar BhattacharyaIUCAA
http://www.iucaa.ernet.in/~astrosat/
LAXPCUVIT
SXT
CZT
SSM
Phased Array Antenna
Star Sensors
http://www.iucaa.ernet.in/~astrosat/
UVIT capabilities
FUV: 130 - 180 nm (~7-10 eV)NUV: 200 - 300 nm (~4.1-6.2 eV)VIS: 320 - 550 nm (~2.2-3.9 eV)
Effective Area: ~15 cm2 (FUV) ~50 cm2 (NUV / VIS)
Typical sensitivity: mAB ~ 20
Typical resolution: ~ 1.8 arcsec
HEXTE, ISGRI
LAXPC
SXT
LAXPC
CZTI
SXT
LAXPC
ASTROSAT Key Niche
• UV imaging
• X-ray timing: Only mission with high resolution timing capability immediately after RXTE
• Simultaneous multiwavelength variability: UV-X ray correlation
• Sensitive hard X-ray spectroscopy: e.g. Cyclotron lines
• Wideband spectrum: UV, 0.3-150 keV
ASTROSAT will be an observatory class mission, driven by proposals received from the user community
http://www.iucaa.ernet.in/~astrosat/
ASTROSAT Key Niche
• UV imaging - study of star forming regions, extinction, mid-redshift Ly-break galaxies, SFR history
http://www.iucaa.ernet.in/~astrosat/
Galaxy images from the GALEX satellite
ASTROSAT will be able to obtain imageswith 3-4 times better resolution
ASTROSAT Key Niche
• X-ray timing: Only mission with high resolution timing capability immediately after RXTE
• Simultaneous multiwavelength variability: UV-X ray correlation
Detailed analysis of intensity variations as a function of time,energy and other properties of the system
=> Mass and spin of black holes and neutron stars. State of matter at high density. GR effects.
http://www.iucaa.ernet.in/~astrosat/
Timing with ASTROSAT
• Periodic phenomena: pulsars, orbital variations• Quasi-periodic/aperiodic variations• Correlation of power spectra with energy spectra and luminosity states• Large range of time scales: sub-ms to months• Large range of energy scales: 10-3 to 102 keV
http://www.iucaa.ernet.in/~astrosat/
Energy dependence of High FrequencyQuasi-Periodic Oscillation amplitude4U 1608-52Berger et al 1996; Gilfanov et al 2003
http://www.iucaa.ernet.in/~astrosat/
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Time (s)
Burst Oscillations
Time (s)Strohmayer et al 1996
Thampan, Bhattacharya, Datta 1998
Upper QPO frequency from innermost allowed orbit: ISCO / NS radius
=> Constraints on NS EOS
Major emission componentsin accreting Black Hole sources
Zdziarski & Gierlinski 2004
XTE J 1550-564 Spectral / Luminositystates of accreting BH
Zdziarski & Gierlinski 2004
XTE J 1550-564 Spectral / Luminositystates of accreting BH
Power spectrum of intensity variation isseen to depend on the spectral state
Zdziarski & Gierlinski 2004
XTE J 1550-564 Spectral / Luminositystates of accreting BH
Transition from hardto soft state appearsto be correlated withthe launching of jets
Power spectrum of intensity variation isseen to depend on the spectral state
Zdziarski & Gierlinski 2004
XTE J 1550-564 Spectral / Luminositystates of accreting BH
Transition from hardto soft state appearsto be correlated withthe launching of jets
Power spectrum of intensity variation isseen to depend on the spectral state
ASTROSAT will haveexcellent capability tostudy this phenomenology
ASTROSAT Key Niche
• Sensitive hard X-ray spectroscopy: e.g. Cyclotron lines
http://www.iucaa.ernet.in/~astrosat/
Astrosat will be a verysensitive instrument for cyclotron lines. Phaseresolved spectroscopy tomap magnetic structures inaccreting pulsars can be carried out
Paul 2004Vigelius & Melatos 2008
ASTROSAT Key Niche
• Broadband spectroscopy: e.g. Magnetar spectra
http://www.iucaa.ernet.in/~astrosat/
Magnetar spectra aremulti-component, time-variable and poorly understood.
Simultaneous broadbandcoverage essential fordetailed study
-6-8 -4 -2 0-6 2 4
-18
-16
-14
-12
-10
log E (keV)
log
E F(
E) (
erg/
cm2 /
s)
den Hartog et al 2006
Multiwavelength science: AGN :: Disk photons+Compton
log
Flux
log photon energy
Spectral pivoting and Comptonization cycle - correlated variability expected - No detailed study so far
UV
X
Multiwavelength science: AGN :: Blazars
3C 279
Synchrotron:seed photons
Compton:upscattered photons
Multiwavelength science: CVs :: Accretion on Magnetic WDs
Multi-temperature plasma - Multiple emission components
- Simultaneous multiwavelength spectra can reveal the ongoing physical processes
hard X-rays
white dwarf
shock
cold supersonic flow
hot postshock
flowsoft X-rays/extreme UV
optical/IRcyclotronradiation
ASTROSAT Key Niche
• Wideband spectrum: UV, 0.3-150 keV
http://www.iucaa.ernet.in/~astrosat/
Simulated Broadband spectrum of Coma Cluster
Synergy with NuSTAR
CZTI
SXT
LAXPC
CZTI
SXT
LAXPC
NuSTAR
Synergy with NuSTAR
• Extension of spectral coverage• Timing-spectroscopy complementarity• TOO services• Cross calibration
Synergy with NuSTAR
• Extension of spectral coverageNuSTAR will have excellent spectral sensitivity in hard X-ray bands over long exposures
ASTROSAT can provide valuable extension to soft X-rays
For a typical E-2 photon spectrum NuSTAR andASTROSAT SXT will have similar count rates
AGN / Magnetars / Galaxy clusters / UV-X studies of starbursts........
Synergy with NuSTAR
• Timing-spectroscopy complementarity
ASTROSAT
Large AreaHigh countrateHigh background
Good for Timing
NuSTAR
Low backgroundHigh spectral resolnSmaller countrate
Good for SpectroscopyThese two missions may participate in joint spectral-timing and
monitoring campaigns, e.g. of BH sources / AGNs / Magnetars / YSOsCyclotron lines important for both missions: phase resolved / phase averaged
Synergy with NuSTAR
• TOO services
Many opportunities will arise for TOO observationsby both missions. Multispectral coverage important.Higher resolution of NuSTAR can help resolve sourceconfusion in ASTROSAT.
Synergy with NuSTAR
• Cross Calibration
Simultaneous availability of the two missions willprovide an excellent opportunity for cross-calibration in overlapping energy bands. Will be helpful in calibrating the complex response of LAXPC
Concluding Remarks
• Both ASTROSAT and NuSTAR will open up several unique science opportunities
• These two missions share several common goals. Simultaneous availabiliy will enhance the science of both missions
• Should explore means of initiating a collaborative science programme
Thank you