High Energy Universe Viewed Through Astrosat P C

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 ke. V to 100 ke. V for timing and spectral studies with 3 X-ray instruments. • Large collecting area in 2 -20 ke. V ( ≥ 6000 cm sq. ) for timing studies in X-rays. • Largest area detector for hard X-ray studies ( ~ 5000 cm sq. at 50 ke. V ), 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 cm 2 at 20 ke. V, FOV =10 X 10, sensitive in 3 -80 ke. V band with low spectral resolution (E/ΔE ≈ 5 to 12). 2. CZT Imager : X-ray detector Cd. Zn. Te (Cadmium-Zinc-Telluride) array with a coded mask aperture having Aeff = 500 cm 2 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 ke. V with A eff ≈ 200 cm 2 at 1 ke. V.

4. SSM : Scanning Sky Monitor (SSM) using 3 PSPCs with coded mask aperture , each with Aeff = 30 cm 2 and energy band of 2 -20 ke. V. 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. Auplated SS wires under tension used for anodes.

One LAXPC unit undergoing tests in Thermovac Chamber to simulate space-like environment.

Soft X-ray Imaging Telescope employs Xray Reflecting Optics and an X-ray CCD to record X-ray Image and measure X-ray energy. CZT Imager on Astrosat For Hard X-ray Spectroscopy and Imaging Sectional View of the Two Telescope configuration of the Ultra Violet Imaging Telescope (UVIT) for the Astrosat mission

UVIT Characteristics Two similar coaligned telescopes Primary Mirror aperture : Secondary 38 cms 14 cms Focal length : 503 cms f/ratio : 13 Configuration : RC with focal plane corrector 90% energy : ≈ 1” Corrected field : 0°. 5 Passband: 120 -180 nm Channel II 180 – 300 nm Optical Detector : Channel I 350 -650 nm 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 + Mg. F 2

Components in each Detector Intensifier (DM) Imaging area : ~ 40 mm f QE : > ~5% in band centre Pos. res. < 100 mm Exposure : 10 -1000 m. Sec Frame rate : > 20 Hz Gain : 2000 – 20, 000 e-/g Safety : electronic gating Fiber Optic Taper High Voltage supplies (HVU) CCD/CMOS (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 (M 61) in Optical, UV and Xray 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 3 C 273 over 20 year period in different spectral bands Fig. 2. Examples of light curves from the 3 C 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 ke. V and in the 20– 70 ke. V 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, 411425, 2008 )

Multiwavelength light curves from intensive monitoring of the BL Lac object PKS 2155304 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 UVW 1 and X-ray (0. 6– 10 ke. V) light curves over the 160 days of Swift observations of Black Hole source XTE J 1817 -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 (Ap. J, 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-P 3.

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 ke. V in Black Hole and Neutron star binaries is an unexplored area. QPOs above 10 ke. V detected so far only in 3 BH Binaries. k. Hz QPOs above 10 ke. V reported so far only in GRO J 1655 -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) M 82 X-1: QPO = 54 -166 m. Hz NGC 5408 X-1: QPO = 20 m. Hz 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 J 10. 34+396. QPO Period= 3733 s M Gierliński et al. Nature 455, 369 -371 (2008) doi: 10. 1038/nature 07277 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 hole 18. A tentative frequencymass 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 frequencies are 2 f 0 and 3 f 0 (the fundamental is not seen). This relation yields the black hole mass in RE J 1034+396 of 6. 9× 10 e 6 or 1. 0× 10 e 7 M☼, depending on whether the observed periodicity corresponds to 2 f 0 or 3 f 0,

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 ke. V 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 4 U 1705 -44 ( Astro-ph 0909. 2572 by Gilfanov)

Energy Spectrum of SNR Cas A in o. 5 -100 ke. V X-ray measurements above 20 ke. V crucial for detecting Non-thermal spectral component in X-ray binaries, SNRs, AGNs and Cluster of Galaxies.

Average Spectrum of Intermediate Polars. Best fit k. T ~ 20 ke. V 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 ke. V

Energy Spectra of Magnetars measured with instruments onboard Suzaku in 0. 8 -70 ke. V. A Blackbody thermal component with k. T ~ 0. 5 -1 ke. V 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 ke. V 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 ke. V) dependence of the fundamental cyclotron resonance energies in binary X-ray pulsars, using Gaussian absorption modeling. The other data points for A 0535+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 ke. V as the second harmonic), and Kendziorra et al. (1994; 3. 8 × 1037). The results on 4 U 0115+63 and X 0331+53, both assuming a distance of 7 kpc, are from Nakajima et al. (2006) and Nakajima (2006), respectively.

Simulation of Cyclotron Lines from Pulsar 4 U 0115+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 ke. V with LAXPCs of A ~ 6000 cm -2 in. 3 -20 and ~ 5000 cm-2 in 20 -60 ke. V bands. Largest area ever used for hard Xray 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 ke. V band. • Simultaneous observations with co-aligned 3 X-ray Instruments covering 0. 3 -100 ke. V 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 ~ 21 st magnitude. Detection and monitoring of transient and persistent X-ray sources with SSM.