Overview of Science with Astrosat

Talk at LAXPC Workshop at BF

Hyderabad , December 15 , 2014

P.C.Agrawal

UM-DAE Center for Excellence in Basic Sciences, Mumbai

University Campus, Vidhyanagari,Mumbai

ASTROSAT : A Broad Spectral Band Indian

Astronomy Satellite

An Indian National Space Observatory

A Collaborative Project of

Tata Institute of Fundamental Research (TIFR), Mumbai

ISRO Satellite Centre (ISAC), Bangalore

Indian Institute of Astrophysics (IIA), Bangalore

Inter-University Centre for Astronomy & Astrophysics, Pune.

Raman Research Institute, Bangalore

Canadian Space Agency, Canada

Leicester University, U.K.

With participation of

Many Indian Universities and research centres

•IXAE on IRS-P3

• Launched on March 21,

1996 from SHAR

• IXAE PPCs on top deck

with remote sensing

instruments

• Stellar mode observations

for about 2/3 months in a

year

• IXAE switched off after 5

yrs of operation due to

depletion of fuel for

pointing control

Quasi-regular Bursts from GRS 1915+105 observed with

PPCs on IXAE (Paul et al. ApJ Lett ,1998)

Salient Features of Astrosat

• Multi-wavelength observations with four co-aligned

instruments covering Visible, Near-UV, Far-UV, Soft X-ray

and Hard X-ray bands.

• Broad Spectral coverage in X-rays from 0.5 keV to 100

keV for timing and spectral studies with 3 X-ray

instruments.

• Large collecting area in 2-20 keV ( ≥ 6000 cm sq. ) for

timing studies in X-rays.

• Largest area detector for hard X-ray studies ( ~ 5000

cm sq. at 50 keV ), important for studying high frequency

QPOs and non-thermal component in Black Hole sources.

•

• High angular resolution telescopes ( ~ 2 arc sec ) in the

UV region. Two telescopes each of 38 cm aperture, one in

Visible and Near-UV and other in Far- UV with photon

counting detectors for high sensitivity observations.

• Soft X-ray Imaging Telescope and CZT Imager for

medium energy resolution spectral studies and

localization of Transients in soft and hard X-ray bands.

• A Scanning Sky X-ray Monitor to detect and monitor

Transients and known objects.

• High time resolution (10 µs ) and high count rate

capability with LAXPC instrument.

Astrosat Instruments

Four X-ray Astronomy Instruments and one Ultraviolet Instrument

With two Telescopes

1. LAXPC : Large Area X-ray Proportional Counters with Aeff ≈ 6000

cm2 at 20 keV, FOV =10 X 10, sensitive in 3-80 keV band with low

spectral resolution (E/ΔE ≈ 5 to 12) .

2. CZT Imager : X-ray detector CdZnTe (Cadmium-Zinc-Telluride)

array with a coded mask aperture having Aeff = 500 cm2 and

medium spectral resolution (E/ΔE ≈ 20 to 30).

3. SXT : Soft X-ray Imaging Telescope using conical-foil mirrors

with medium angular (~3' ) and spectral (E/ΔE ≈ 20 to 50)

resolution in 0.3-8 keV with A eff ≈ 200 cm2 at 1 keV.

4. SSM : Scanning Sky Monitor (SSM) using 3 PSPCs with

coded mask aperture , each with Aeff = 30 cm2 and energy

band of 2-20 keV.

5. UVIT : Ultraviolet Imaging Telescope (UVIT) has two

similar telescopes each with 38 cm aperture primary mirror

and photon counting imaging detectors covering

simultaneously

FUV ----- 130 – 180 nm 28 arc min field

NUV ------ 200 – 300 nm

Visible ----- 320 – 550 nm

A Charged Particle Monitor (CPM) as an auxiliary

instrument for the control and operation of the Astrosat

Instruments.

LAXPC X-ray detector Anode Assembly with veto layer on 3 sides mounted on the back

plate. 60 Anode cells are arranged in 5 layers to make the X-ray detection volume. 37

Micron dia. Au-plated SS wires under tension used for anodes.

• LAXPC has high detection efficiency up to ~ 80 keV ( > 50 % upto 70 keV)

• Deep Detector (15 cm arranged in 5 layers each 3 cm deep vs 3.3 cm for

the PCA on RXTE

• Xenon filled at a pressure of 2 atmosphere

A view of the LAXPC

Instrument used for

assessing the

performance of

LAXPCs in a Balloon

flight launched on

April 16,2008 from BF

Hydearabad reaching

a ceiling of 41 km (2.5

g/ cm -2 of residual

atmosphere. It used 2

LAXPCs similar to

Astrosat LAXPCs but

with FOV of 3 deg X 3

deg.

LAXPC A Count rates as a function of time. Increase

in count rates in Cygnus X-1 observations can be

clearly seen.

Instruments are technically complex and challenging,

they are not commercially available. In India the design

and development of instruments have to be done in

house as expertise and experience available only with

few persons. Fabrication of flight hardware also mostly

done in house only.

X-ray CCD

mounted on

Thermoelectr

ic Cooler to

be used for

the SXT

30 December 2014 16

CCD Data (CCD +TIFR Electronics)

5.9 and 6.4 keV peaks

Si escape peaks

3.70 and 4.15 keV

Isolated pixels only

Resolution ~150 eV

(2.5% at 6 keV)

CZT Module characterization

Estimated Effective Areas of UVIT

Effective area of Astro-H at different energies for the 4

instruments aboard (Takahashi et al. 2014)

X-ray light curve

and pulsations

from NuStar

J09551+6940.8

coincident with

known ULX in M82 .

(Pulsation P= 1.37

s , Orbital P= 2.51

days)

Bachetti et al.

Nature, 2014

Study of High Energy Universe by X-ray and UV Observations

All types of Galactic and Extragalactic objects are UV and X-ray sources

Brightest Galactic Sources in UV and X-rays : Compact Stars in Accreting X-ray Binaries :

Neutron Stars { Both have high luminosity in X-rays

Black Holes { and are also visible in UV

White dwarfs ( Bright UV objects as T is high)

Supernova Remnants :

About 200 SNRs in our galaxy .

Shock heated gas (T ~ 10 5 - 10 7 ) emits UV and

X- rays

Extragalactic Sources :

Intermediate –Mass Black Holes in galaxies

AGNs ( Quasars, BL Lacs , Seyfert Galaxies ) : Powered by massive ( 10 7- 10 9 M O ) accreting Black

Holes in their nuclei

Accretion Disks Around BHs emit UV and X-rays . There is

excess UV from AGNs (called UV Bump )

Cluster of Galaxies : Thermal emission Lx ~ 10 44 ~ 10 46 ergs per sec

Detection and study of Non-Thermal Component

Star Burst Galaxies and Star Forming Regions :

Nurseries of young stars and pre-main sequence stars

that are copious UV and X-ray sources

Astrosat Science Objectives

Multiwavelength Observations

• ASTROSAT will be a powerful mission for Multiwavelength

studies of various types of sources using 5 co-aligned telescopes

covering broad X-ray , near- UV , far- UV and Optical bands.

• AGNs will be prime targets for this as only a small number of bright

AGNs studied so far.

• Correlated UV , Optical and X-ray variations , measure time lags

and do reverberation mapping.

• Broad band studies of X-ray binaries and Magnetic CVs is

important for probing origin of components of emission

Multiwavelength light curves from intensive monitoring of the BL Lac object PKS 2155-

304 in 1991 November (Edelson et al. 1995). X-ray data are from the Rosat PSPC; UV

data are from the IUE SWP (short wavelength) and LWP (long-wavelength)

spectrographs; optical data are from the FES monitor on IUE. The emission is closely

correlated at all wavelengths, and the X-rays lead the UV by ~ 2-3 hours.

Comparison of the NUV UVW1 and X-ray (0.6–10 keV) light curves over the 160 days of

Swift observations of Black Hole source XTE J1817-330. The NUV flux most closely

tracks the X-ray power-law emission and does not track the total X-ray flux or the X-ray

disk flux (ApJ,666,1129,2007)

Astrosat Sience Goals High resolution timing studies :

• Periodic and chaotic variability, Evolution of pulse and

orbital periods in X-ray binaries, Accreting Millisec Pulsars

and AXPs.

Size of emission region, Nature of X-ray source, orbital parameter ,

rotation rate of neutron star, Accretion Torque acting on it, idea about

magnetic field etc

• Detection and measurements of of low and high

frequency QPOs in soft and hard X-ray bands in Black

Hole and other X-ray Binaries .

Accretion process , innermost stable orbit of matter in accretion disk

• High Freq. QPOs studies put constraints on mass and

spin of Black Holes.

Dependence of NS Spin-up rate on X-ray flux (Bildsten et al.

1997)

Spin period evolution of GX 1+4 (Gonzalez-Galan et al. A&A

2011)

Spin-up/ Spin-down transition in disk accreting NS in the X-

ray Binary 4U 1626-67 (Camero-Arranz et al. ApJ,708, 2010)

LMXB with disk fed accretion, P= 7.66 sec

Light Curve of LMXB Transient Aql X-1 can be explained by

Propeller effect (Campana 2014)

High Frequency QPOs in BH X-ray Binaries from PCA on RXTE

QPOs in black hole

transient XTE J1817-

330 (Roy et al.

MNRAS 2011).

Panel (a) 2-8 keV (b)

8-14 keV and (c) 15-

25 keV

QPOs detected in XMM-Newton light curve of Narrow-line

Seyfert 1 RE J10.34+396. QPO Period= 3733 s

M Gierliński et al. Nature 455,

369-371 (2008)

doi:10.1038/nature07277

High-frequency QPOs seen in

several BHBs occur in pairs

with the frequency ratio of 3:2.

These frequencies appear to

be stable and are regarded as

a signature of strong gravity in

the vicinity of a rotating black

hole18. A tentative frequency-

mass relation, f 0 = 931

(M/M☼)-1 Hz, can be derived

from three objects. This

relation yields the black hole

mass

in RE J1034+396 of 6.9×10e6

or 1.0×10e7 M☼, depending

on whether the observed

periodicity corresponds to 2f0

or 3f0,

The solid line denotes the relation, f (Hz) = 1862(MBH/M⊙)−1 derived from three X-ray

binaries (Remillard & McClintock 2006). The long-dashed line denotes the relation, f (Hz)

=2030.8(MBH/M⊙)−1 for a model of 3:2 resonance and spin parameter a = 0.996; the

dotted-dashed line denotes the relation, f (Hz) =3068.9(MBH/M⊙)−1 for a model of 3:1

resonance and spin parameter a = 0.996; dotted line denotes the Kepler frequency for a

non-spinning Schwarzschild black hole at the innermost stable circular orbit.

Relation

between QPO

Frequency and

BH Mass (Zhou et al. ApJ

Lett, 2014)

Astrosat Science Goals

Broad band Spectral measurements : • Spectra of the continuum emission from all classes of UV

and X-ray sources • Emission and absorption features with medium energy

resolution capability in 0.3 – 100 keV spectral band with 3 co-aligned X-ray instruments.

• Understand the Complex Multi-component energy Spectra

of galactic and extragalactic Black Hole sources to understand the origin of radiation from various processes.

• Measuring non-thermal spectral component in Accreting

NS and BH Binaries,SNRs and AGNs

Astrosat Science Goals

Broad band Spectral measurements :

• Black Body and Thermal Components usually dominant in most sources below a few keV.

• Non-thermal emission prominent in BH Binaries

and AGNs above 10 keV.

RXTE-PCA Energy Spectrum of HMXB A 0535+26 during

quiescence (Rothschild et al. ApJ,2013)

Energy Spectra of Black Hole Binary Cyg X-1 and Neutron Star

Binary 4U 1705-44 ( Astro-ph 0909.2572 by Gilfanov et.al. )

Spectrum of BH Binary GX 339-4 in hard state with Swift-XRT (0.8-

8keV),RXTE-PCA (3.6 – 25 keV) and RXT-HEXTE (17 – 240 keV)

(a) Observed spectrum (b) Spectrum fitted with a thermal component,

a reflection component and in iron emission line (Tomsick et al. ApJ.

2006)

Astrosat Science Goals

• Detection and profiles of Cyclotron Resonance

Absorption Features in the spectra of X-ray Pulsars

Cyclotron features deteted so far in ~ 23 pulsars

range in 10 keV ( ) to 78 keV ( )

• High resolution ( ≤ 2 arc sec ) UV imaging studies

of Star Burst Galaxies, Nornmal Galaxies ,AGNs,

Hot stars, SNRs etc.

• Deep UV survey of selected regions of sky

• X-ray scans of Galactic Plane and Center for

detection of new transients and other variable sources

• X-ray Monitoring of Sky for detection of Transients,

Bursts and Flaring activity and studies of persistent

sources

Energy spectrum of the accreting pulsar in V 0332+53 at two

intensity levels measured with the INTEGRAL. Two Cyclotron

lines are clearly seen (Tsygankov et al. MNRAS, 371,2006)

P (spin) ---4.37 s , P (orbit) ---- 34.7 days

Cyclotron line

at 26 keV,

harmonics at

~50 and ~ 73

keV

L (x)

anticorrelated

with line

energy

Centroid Energy of phase averaged Cyclotron line from

Her X-1 since its discovery (Staubert et al. A&A, 2014)

Astrosat Mission Characteristics

• Three axes stabilized well proven satellite bus using 3 gyros and 2 star

trackers for attitude control by reaction wheel system with a Magnetic

torquer

• Pointing accuracy of about 1 arc sec.

• Mission life of at least 5 years. Circular orbit of 600 km altitude and

inclination of ≤ 8°.

• Launch by well proven Indian Polar Satellite Launch Vehicle (PSLV) from

Satish Dhawan Launch Center at Shriharikota (India).

• Mass of satellite 1548 kg including 870 kg mass of science payloads.

• Data stored onboard in a 120 Gbits Solid State Recorder already proven

in an earlier mission.

• Data transmission by two X-band carriers at rate of 105 Mbits per sec.

Conclusions

• Astrosat will enable timing observations with 10 µs accuracy in a broad spectral band of 3-80 keV with LAXPCs of A ~ 6000 cm -2 in. 3-20 and ~ 5000 cm-2 in 20-60 keV bands. Largest area ever used for hard X-ray studies.

• Medium energy resolution capability of CZT for accurate

spectra and detection of cyclotron features.

• SXT for imaging and spectral studies for 0.3-8 keV band.

• Simultaneous observations with co-aligned 3 X-ray Instruments covering 0.3-100 keV region to construct spectra of sources.

• High angular resolution telescopes ( ~ 2 arc sec ) in

the UV region. Two telescopes each of 38 cm aperture,

one in Visible and Near-UV and other in Far- UV with

photon counting detectors for high sensitivity ( 21 mag or

better) observations.

• Soft X-ray Imaging Telescope and CZT Imager for

medium energy resolution spectral studies and

localization of Transients in soft and hard X-ray bands.

• A Scanning Sky X-ray Monitor to detect and monitor

Transients and known objects.

• High time resolution (10 µs ) and high count rate

capability with LAXPC instrument.

Allocation of Observing Time and Data Sharing Policy

• Performance Verification Phase (First 6 months)

All Observations by Instrument Teams

• Guaranteed Time for Instrument Teams ( Next 6 months)

• First Year of Regular Observations in Pointed Mode

35% Time for Indian Astronomers, 5% GT for CSA , 3% GT for

Leicester University, 5% TOO, 2% TBD, 50% GT for Instrument

Teams

• Second Year of Regular Observations in PM

45% Time for Indian Astronomers on Competitive basis.

10% Any International Astronomer on Competitive basis.

30% GT for Instrument Teams, 5% GT for CSA, 3& GT for LU ,

5% TOO, 2% TBD

•

Allocation of Observing Time and Data Sharing Policy

•Third Year Onwards

5% GT for CSA, 3% GT for LU , No Guaranteed time for Instrument

teams.

• All Science Data in a National Space Science Data Archival Centre

for ISRO after a TBD period (12 months except PV and GT data)

accessible to any one in the world.