p.c.agrawal um-dae center for excellence in basic …laxpcworkshop14/presentations/science...
TRANSCRIPT
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.