Two Topics: Prospects of detection of Hard X- rays from I. Active Cool Stars, II. Clusters of galaxies. K.P. Singh (TIFR, Mumbai)

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1 Two Topics: Prospects of detection of Hard X- rays from I. Active Cool Stars, ì II. Clusters of galaxies LAXPC Hyderabad December 15 17, 2014 K.P. Singh (TIFR, Mumbai)

2 The Sun an active star in X- rays An impulsive flare

3 The Sun LDE Flare

4 Loop Models for Solar X- ray Flares

5 The Neupert Effect The Sun The energe8c electrons responsible for F (t) by thick- target HXR collisional bremsstrahlung are the main source of hea8ng and mass supply (via chromospheric evapora8on) of the SXR- emigng hot coronal plasma.

6 The Neupert Effect Active Cool Stars Proxima Centauri AB Doradus A Fuhrmeister & Lalitha 2011 Lalitha et al. 2013

7 BAT Flare in II Peg Osten et al. 2007

8 II Peg Flare spectrum Osten et al. 2006

9 Hard X-Ray Polarimetry X4.8 Flare of 23-July FLR kev µ p = 0.10 ± 0.04 Π 18% Φ = 79 ± 3 Counts Scatter Angle (η) kev Polarization Mark K P Singh McConnell, (TIFR) UNH

10 X- rays from Active Cool Stars: ASTROSAT Simulations for 20 ks exposures S. Lalitha

11 X- rays from Active Cool Stars: ASTROSAT Simulations for 20 ks exposure S. Lalitha

12 Solar vs. Stellar non- thermal vs thermal Predictions for ASTROSAT 20 ks S. Lalitha

13 Solar vs. Stellar non- thermal vs thermal Predictions for ASTROSAT 20 ks Model parameters Name Sp. type D (pc) log EM (cm -3 ) T (MK) log L XT ( erg/s) Quiet Flare Proxcen M6Ve AD Leo M4.5Ve EV Lac M4.5V AB Dor K0V HR 1099 K II Peg K2IV S. Lalitha

14 INTEGRAL detections of hard X- rays from Active Cool Stars At least three INTEGRAL sources have been identified in the 70-month BAT Catalog as being of the RSCVn type cool stars based on the optical spectra of the candidate stars in the field of view. Name R (mag.) d(pc) Lx(10 30 ergs/s) kev IGR J IGR J <4600 IGR J ( kev) 100 (20-100keV) Extremely bright probably caught during flaring episodes! Similarly a SWIFT transient J has been identified with an M-dwarf flare star.

15 End of Part I

16 II. Search for Non- thermal hard X- ray emission from Clusters of galaxies ì Astrophysics with Hyderabad 2015

17 Motivation The X-ray emitting thermal plasma in a virialized cluster loses most information on how the formation proceeded due to the dissipative processes driving the plasma towards a Maxwell- Boltzmann momentum distribution characterized by its temperature only. Non- equilibrium distributions of cosmic rays preserve the information about their injection and transport processes much better, and thus provide a unique window of current and past structure formation processes. Information about these nonequilibrium processes is encoded in the spectral and spatial distribution of cosmic ray electrons and protons. Radiative loss processes of these non-thermal particle distributions produce characteristic radio synchrotron, hard X-ray inverse Compton, and K P Singh hadronically (TIFR) induced γ-ray emission.

18 Motivation Non-thermal Radio emission is seen as: Radio Relics: Have a high degree of polarisation, are irregularly shaped and occur at peripheries of the clusters -- can be attributed to merging or accretion shock waves. Radio Haloes: Resemble the regular morphology of the X- ray emitting intra-cluster plasma and are poorly understood. Where is the non-thermal X-ray and γ-ray emission?

19 Clusters of galaxies: Physical Processes & Observables Pfrommer, Enßlin & Springel, MNRAS, 2008

20 Non- thermal processes

21 Hard X- ray (20-80 kev) Tails: Balloon+Satellite based measurements Beppo-SAX: Nevalainen et al Relaxed Fig. 3. The non-thermal signal and 1σ uncertainties in PDS kev band after subtraction of the contributions from the background, thermal gas and AGN in the field, and after propagatinguncertaintiesduetothesesubtractions. The dotted vertical line separates the relaxed clusters (left) from the rest (right).

22 Swift/BAT: Jointly with XMM- Newton Ajello et al. 2009, Clusters studied: Perseus, A3266, A754, Coma, A3571, A2029, A2142, Triangulum, Ophuchius, A2319; A85, A401, Bullet, PKS , A1795, A1914, A2256, A3627 (Norma), A3667, A2390. All best described by multi-temp thermal model except Perseus and Bullet (4.4σ) which show hard X-ray excess consistent with Chandra Observations for Bullet, and AGN: NGC 1275 in Perseus.

23 Suzaku + XMM: Coma Cluster (A1656) Wik et al. 2009; Also see: Suzaku observations of X-ray excess emission in the cluster A 3112 T. Lehto et al à Basically: Cannot rule out the presence of NT emission!! FIG.5. Suzaku HXD-PIN spectrum (E > 12 kev) and the combined XMM spectrum (E < 12 kev) corresponding to the spatial sensitivity of the PIN. Shown as solid lines are the best fit models for a single temperature thermal component plus a non-thermal component. The thermal model ( APEC", green) is nearly coincident with the data, though falling below it at higher energies. The non-thermal model ( Power Law", light blue) is the faintest model component for both spectra, and the photon index is fixed atγ =2.0. The other two components are described in Figure 4.

24 Ophiuchus: 2 nd brightest X- ray cluster (kt ~ 9-10 kev) Integral Detection at 4 to 6.4σ level: Eckert et al normalized counts/sec/kev Consistent with Suzaku (Fujitsa et al. 2008), Beppo-SAX, Swift/ BAT upper limits! χ channel energy (kev) Fig. 7. JEM-X/ISGRI combined spectrum in the 3-80 kev band. The solid line is a fit to the 3-20 kev part of the spectrum with asingle-temperaturemekalmodel.thebottompanelshows the residuals from the model. The hard X-ray excess is clear.

25 Abell 2319: A well- known example of merging clusters with a giant radio halo Suzaku: upper limit on non-thermal inverse Compton component is erg s 1 cm 2 in the kev band, which means that the lower limit of the magnetic field is 0.19 µg (Sugawara et al. 2009). Derived from the ratio of measured IC flux density in X-rays to the measured Sync flux density in the radio using Blumenthal and Gold (1970) see below dw Syn dν Syn dt = 4πN 0e 3 B (p+1)/2 m e c 2 ( 3e 4πm e c ) (p 1)/2 a(p)ν (p 1)/2 Syn, (1) dw IC dν IC dt = 8π2 r 2 0 c 2 h (p+3)/2 N 0 (kt CMB ) (p+5)/2 F(p)ν (p 1)/2 IC, (2)

26 Chandra: non- thermal- like extended X- ray emission from massive, merging, radio- halo clusters Sample of X-ray luminous clusters with large, extended radio halos (Feretti & Giovannini, 2007). Chandra Spatio-spectral Observations of 7 (+ 5 non-halo clusters) - Million & Allen, 2009 Each spatial region had at least 10K counts in spectrum. Detections in four halo clusters: A2319, A2255, A665, 1E (Bullet) spectra summed over all regions Non-detections in three halo clusters: A2163 (Ota et al.2013: Suzaku detection in kev!), A2219, A2744 Cluster N H,Gal #regions N H mean PL Flux Abell / ergs s 1 cm 2 5 Abell / Abell / Abell / Abell / Abell / E / Detection in one non-halo cluster: A2029 No detection in 4 non-halo clusters: A576, A1795, A478, A2204

27 Chandra: Bullet Cluster Surface Brightness and Temperature (kt) maps: Mean kt is ~ 14 kev!

28 Chandra: The Bullet Cluster non- thermal surface brightness and PL index Figure 2. (a) left panel: Spatial map of the surface brightness (in erg cm 2 s 1 arcsec 2 )ofnon-thermal-likex-rayemissioninthebullet Cluster, 1E (z =0.297). A power-law component is only included in regions where it is statistically required at greater than 90 per cent significance (Section 3.2). The 1.34 GHz radio surface brightness contours from Liang et al. (2000) are overlaid in black. (Radio point sources have been removed). (b) right panel: Map of the photon index of the power-law components, with the radio surface brightness contours overlaid. Only regions with non-thermal surface brightness greater than ergs s 1 cm 2 arcsec 2 are shown in this map. Each spatial region has 10 4 net counts in the kevchandraband.

29 Chandra: The Bullet Cluster RESULT: Spatial correlation between the regions of the brightest non-thermal radio halo emission, brightest thermal X-ray emission, and strongest non-thermal-like X-ray signatures in the central regions of 1E

30 Bullet Cluster: NuStar (266 ks): Wik et al Very hot kt ~ 15.3 kev, and no evidence for a NT component above 20 kev

31 s 1 ) 7 10 Fermi era: Ackermann et al clusters from 18 months of data F > 0.1 GeV ( ph cm 2 s 1 ) F > 0.1 GeV ( ph cm C129 A2744 A0085 A3376 A0754 A3571 A1367 AWM7 A1914 Antlia A2029 Bullet A2142 A2163 Centaurus Coma A2199 Fornax A2256 Hydra A2319 M49 Pinzke & Pfrommer 2010 s 1 ) F > 0.1 GeV ( ph cm Donnert et al EGRET 0.95 CL LAT 0.95 CL MACSJ0717 NGC5044 NGC5846 NGC4636 NGC5813 Norma Ophiuchus Perseus RXJ1347 Triangulum Virgo

32 Summary & Challenges ahead The presence of non-thermal hard X-ray emission in clusters of galaxies remains controversial. Existing limits on this component suggest a small magnetic field of the order of 0.1µG, which is in stark contrast to the Faraday rotation measurements which demand much stronger intracluster magnetic field of order of a few µg (Clarke,Kronberg,Bo ḧringer,2001;carilli and Taylor,2002). Several possible explanations: Two most likely options in this regard could be the simplest ones: either the reports of detections of nonthermal X-rays are not correct, or they are correct but the nonthermal X-rays are not of IC origin. To establish the presence or absence of this component, we will need: Hard X-ray telescopes with: High Spatial resolution, Wide field, Low-to-medium energy/spectral resolution & Large area

33 Best Targets for Astrosat SXT+LAXPC (& ASTRO- H) 1. The brightest radio relic: The NW relic of Abell The radio halo in the Coma Cluster

34 THANKS!