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