agrawal by wanghonghx

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									   High Energy Universe Viewed Through
                 Astrosat
                       P.C.Agrawal
     Tata Institute of Fundamental Research, Mumbai




Talk at the Chandrayan Symposium at IMSc , Chennai ,
                   January 4 , 2011
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
              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 ( 40 k Counts with PHA and 60 k Counts
without PHA ) 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 =1 0 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 A eff = 500 cm2 and
  medium spectral resolution (E/ΔE ≈ 10 to 15 ).

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 near-uv , far-uv and visible bands.

  A Charged Particle Monitor (CPM) as an auxiliary
  instrument for the control and operation of the Astrosat
  Instruments.
 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 Thermoelectric
Cooler to be used for the SXT




                                               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.
One LAXPC unit undergoing tests in Thermovac Chamber to simulate
space-like environment.
Soft X-ray Imaging
                                                      Sectional View of the
                          CZT Imager on Astrosat         Two Telescope
Telescope employs X-           For Hard X-ray
ray Reflecting Optics
                                                      configuration of the
                         Spectroscopy and Imaging    Ultra Violet Imaging
and an X-ray CCD to
record X-ray Image and                              Telescope (UVIT) for the
measure X-ray energy.                                   Astrosat mission
                                    UVIT Characteristics
                                 Two similar coaligned telescopes
Primary Mirror aperture                   :       38 cms
Secondary                                         14 cms
Focal length                              :       503 cms
f/ratio                                   :       13
Configuration                             :       RC with focal plane corrector
90% energy                                :       ≈ 1”
Corrected field                           :       0°.5
Passband:              Channel I                  120-180 nm
                       Channel II                 180 – 300 nm
                       Optical                    350-650 nm
Detector :                                        Photon counting system
                                                  CPM with appropriate read out
                                                  for getting X & Y
                                                  40 mm x 40 m
Pixel resolution       :                          25 μ
Material of Mirror :                              Zerodur with Al + MgF2
Components
  in each
 Detector


     Intensifier

        (DM)
                               Fiber Optic
                                  Taper                       High Voltage
                                                                 supplies
  Imaging area : ~ 40 mm f                                       (HVU)
  QE :> ~5% in band centre
  Pos. res. < 100 mm
  Exposure : 10-1000 mSec
  Frame rate : > 20 Hz            CCD/CMOS
  Gain : 2000 – 20,000 e-/g
  Safety : electronic gating      (Need High Voltage Power Supplies;
                                           up to 8000 V)
                    ASTROSAT Top Deck Layout
                  SXT                           UVIT


                                                       LAXPC




                                                   CZT




                 SSM



Artist’s View of the Astrosat Multiwavelength
                  Observatory
Study of High Energy Universe by X-ray and UV
                Observations
All types of Galactic and Extragalactic objects
are UV and X-ray sources
Galactic Sources :
 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 :

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 )



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 in campaign mode so far.

•   Correlated UV , Optical and X-ray variations , measure time lags
    and do reverberation mapping.

•    Construct energy distribution curves of AGNs over 5 decades in
     energy
Images of the Active
Galaxy Nucleus of
NGC 4303 (M61) in
Optical,UV and X-
ray bands. The bright
central object is
likely to be a
Massive Black Hole
of 100 million Solar
mass producing
energy by accretion
of matter.
Light Curves of quasar 3C 273 over 20 year period in
               different spectral bands


                        Fig. 2. Examples of light curves from the
                        3C 273 database for the last 23 years of
                        observations, at 5 GHz, 37 GHz, 0.8 mm,
                        in the K band, in the V band, at 5 keV and
                        in the 20–70 keV range (this latter rebinned
                        to 1-month bins).
                        The data during strong synchrotron flares
                        (Flag = 1) are indicated in grey (red in the
                        electronic version) for the optical and IR
                        data sets.

                         ( From S. Soldi et al. A&A, 486, 411-
                         425,2008 )
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.

• 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 .

   High Freq. QPOs studies put constraints on mass and
spin of Black Holes.
Periodicities in Accreting X-ray Binaries (Neutron Star and Black Hole
Systems)

P(spin) ~ msec to ~ 1000 sec , P (orbital) ~ 14 min to 100 days
P (QPOs) ~ 0.1 Hz to ~ 1000 Hz , P (Flicker) ~ 100 ms to 10 mins
P(Precession or disc warping) ~ 10 days to `300 days ( found in some XRBs
e.g. Her X-1 ~ 35 days, Cyg X-1 ~ 300 days)
Sub-second Intensity Variations in the Micro-quasar GRS 1915+105
with the Indian X-ray Astronomy Experiment (IXAE) on IRS-P3 .
       Period vs. Period derivative Diagram for all known Pulsars

                                Red Stars are Magnetars




Big Red Star is the new Magnetar SGR 0418+5729 ( N. Rea et al.,Science,330, 944,
                                    2010 )
                Giant flares from SGRs
LF ~ 1045-1047 erg


                                SGR 1900+14 – Aug. 1998
                                Hurley et al. 1999




                                      SGR 1806-20 – Dec. 2004
                                      Palmer et al. 2005
                                            Recent result
•   Detection of QPOs above 10 keV in Black Hole and
Neutron star binaries is an unexplored area. QPOs
above 10 keV detected so far only in 3 BH Binaries.
kHz QPOs above 10 keV reported so far only in GRO
J1655-40.

•     Do AGNs show Bimodal states similar to that of
Stellar- mass Black Holes ? Repeated observations of
AGNs required to answer this.

•    Search QPOs in AGNs. Reports of a few detections
so far.
QPOs detected in two ULXs (Strohmayer & Mushotzky 03; Strohmayer et al. 07)

M82 X-1: ���� QPO = 54-166 mHz
NGC5408 X-1: ���� QPO = 20 mHz
Properties (rms, coherence, noise, variability)similar to Type C QPOs in BHBs
(0.1-15 Hz). Extrapolating correlations known to exist for BH binaries and
assuming that
 QPO scales inversely to MBH (Mucciarelli et al. 06; Strohmayer et al. 07):
 QPOs detected in XMM-Newton light curve of Narrow-line
    Seyfert 1 RE J10.34+396. QPO Period= 3733 s
                                          High-frequency QPOs seen in
                                          several BHBs occur in pairs
                                          with the frequency ratio of 3:28.
                                          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. Here f 0 is the
                                          fundamental frequency of the
                                          pair, i.e. the observed
M Gierliński et al. Nature 455, 369-371   frequencies are 2f0 and 3f0 (the
(2008) doi:10.1038/nature07277            fundamental
                                          is not seen). 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
               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
Energy Spectra of Black Hole Binary Cyg X-1 and Neutron
Star Binary 4U 1705-44 ( Astro-ph 0909.2572 by Gilfanov)
Energy Spectrum of SNR
Cas A in o.5-100 keV

X-ray measurements above
20 keV crucial for detecting
Non-thermal spectral
component in X-ray binaries,
SNRs, AGNs and Cluster of
Galaxies.
Average Spectrum of Intermediate
Polars . Best fit kT ~ 20 keV



                                                  Energy
                                                  Spectrum of
                                                  Seyfert 1
                                                  Galaxy IGR
                                                  07597 – 3842
                                                  from Integral
                                                  and Chandra/
                                                  XMM-Newton
                                                  data.
                                                  Molina et.al.
                                                  MNRAS (2009)

                                                                  Microquasar GRS 1915+105
                                                                  A & A,494,229,2009
  Power Law index = 1.6, Cut off Energy= 70 keV
Energy Spectra of Magnetars
measured with instruments
onboard Suzaku in 0.8-70 keV.
A Blackbody thermal
component with kT ~ 0.5-1 keV
and a power law component
with photon index ~ 0.4-1.7 fit
the spectra well ( Enoto T. et al.
Astro-ph 1009.2810 ).
                Astrosat Science Goals
•    Measure Magnetic Field of Neutron Stars in X-ray Binaries

     From detection and energy of Cyclotron lines in the X-ray spectra of
     Pulsars. Cyclotron absorption lines in ~ 12 – 60 keV detected in the X-ray
     spectra of ~ 20 X-ray Pulsars

       B ~ ( 2-8 ) 10 12 Gauss
• 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
Luminosity (3–50 keV) dependence of the fundamental cyclotron resonance energies in binary
X-ray pulsars, using Gaussian absorption modeling. The other data points for A0535+262
refer to Wilson & Finger (2005; LX = 1.1 × 1037 ergs s-1), Kretschmar et al. (2005; 0.4 × 1037),
Grove et al. (1995; 3.6 × 1037, assuming 110 keV as the second harmonic), and Kendziorra et
al. (1994; 3.8 × 1037). The results on 4U 0115+63 and X0331+53, both assuming a distance of
7 kpc, are from Nakajima et al. (2006) and Nakajima (2006), respectively.
Simulation of Cyclotron Lines from Pulsar 4U0115+63
Ultraviolet image of Galaxy M 33 with Galex. Credit:
              NASA/JPL-Caltech/GALEX
         Astrosat Mission Characteristics
• Pointing accuracy of about 1 arc sec.
• 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
• 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).
•
                   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.
Obtain multifrequency spectra covering Visible, UV , Soft
X-ray and Hard X-ray regions for a variety of sources.

UV studies and deep UV survey of selected regions and
sources with UVIT to a limit of m ~ 21st magnitude.

Detection and monitoring of transient and persistent X-
ray sources with SSM.

								
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