Two Topics: Prospects of detection of Hard X- rays from I. Active Cool Stars, ì II. Clusters of galaxies LAXPC Workshop @ Hyderabad December 15 17, 2014 K.P. Singh (TIFR, Mumbai)
The Sun an active star in X- rays An impulsive flare
The Sun LDE Flare
Loop Models for Solar X- ray Flares
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.
The Neupert Effect Active Cool Stars Proxima Centauri AB Doradus A Fuhrmeister & Lalitha 2011 Lalitha et al. 2013
BAT Flare in II Peg Osten et al. 2007
II Peg Flare spectrum Osten et al. 2006
Hard X-Ray Polarimetry X4.8 Flare of 23-July-2002 8000 6000 FLR2072301 20-40 kev µ p = 0.10 ± 0.04 Π 18% Φ = 79 ± 3 Counts 4000 2000 0 60 120 180 240 300 360 Scatter Angle (η) 20-40 kev Polarization Mark K P Singh McConnell, (TIFR) UNH
X- rays from Active Cool Stars: ASTROSAT Simulations for 20 ks exposures S. Lalitha
X- rays from Active Cool Stars: ASTROSAT Simulations for 20 ks exposure S. Lalitha
Solar vs. Stellar non- thermal vs thermal Predictions for ASTROSAT 20 ks S. Lalitha
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 1.3 50.69 20 27.30 27.50 AD Leo M4.5Ve 4.7 51.00 20 27.50 27.70 EV Lac M4.5V 5.0 52.30 20 28.65 28.90 AB Dor K0V 14.9 52.30 20 28.75 29.00 HR 1099 K2 14.0 53.00 20 29.40 29.60 II Peg K2IV 40.0 53.05 20 31.65 31.90 S. Lalitha
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) 0.1-2.4 2-10 20-40 kev IGR J18371+2634 12.5 530 5.7 4.4 47.0 IGR J23130+8608 14.7 1500 19.0 3800 <4600 IGR J17198-3020 12.3 350 8.3 (0.3 10 kev) 100 (20-100keV) Extremely bright probably caught during flaring episodes! Similarly a SWIFT transient J063933.6+054918 has been identified with an M-dwarf flare star.
End of Part I
II. Search for Non- thermal hard X- ray emission from Clusters of galaxies ì Astrophysics with LAXPC @ Hyderabad 2015
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.
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?
Clusters of galaxies: Physical Processes & Observables Pfrommer, Enßlin & Springel, MNRAS, 2008
Non- thermal processes
Hard X- ray (20-80 kev) Tails: Balloon+Satellite based measurements Beppo-SAX: Nevalainen et al. 2003 Relaxed Fig. 3. The non-thermal signal and 1σ uncertainties in PDS 20 80 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).
Swift/BAT: Jointly with XMM- Newton Ajello et al. 2009, 2010 20 Clusters studied: Perseus, A3266, A754, Coma, A3571, A2029, A2142, Triangulum, Ophuchius, A2319; A85, A401, Bullet, PKS 0745-19, 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.
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. 2010 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.
Ophiuchus: 2 nd brightest X- ray cluster (kt ~ 9-10 kev) Integral Detection at 4 to 6.4σ level: Eckert et al. 2007 normalized counts/sec/kev 10 4 10 3 0.01 0.1 Consistent with Suzaku (Fujitsa et al. 2008), Beppo-SAX, Swift/ BAT upper limits! χ 2 0 2 4 5 10 20 50 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.
Abell 2319: A well- known example of merging clusters with a giant radio halo Suzaku: upper limit on non-thermal inverse Compton component is 2.6 10 11 erg s 1 cm 2 in the 10-40 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)
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 0657-56 (Bullet) spectra summed over all regions Non-detections in three halo clusters: A2163 (Ota et al.2013: Suzaku detection in 12 60 kev!), A2219, A2744 Cluster N H,Gal #regions N H mean PL Flux Abell 2319 8.09 3/10 8.3 +0.4 0.4 2.0 +0.4 0.3 11 +8 10 12 ergs s 1 cm 2 5 Abell 2255 2.50 2/4 3.01 +1.0 0.7 1.68 +0.19 0.27 5.1 +1.2 1.2 Abell 665 4.33 2/3 2.6 +1.2 1.5 1.63 +0.10 0.21 4.2 +1.4 1.2 Abell 2163-4/17 15.4 +0.4 0.3 1.51 +0.05 0.05 3.9 +1.0 1.0 Abell 2219 1.76 0/8 1.7 +0.3 0.3 - - Abell 2744 1.39 3/6 1.7 +0.4 0.4 1.66 +0.40 0.13 0.4 +0.2 0.3 1E 0657-56 4.89 13/55 4.99 +0.15 0.14 1.50 +0.05 0.05 0.95 +0.10 0.11 Detection in one non-halo cluster: A2029 No detection in 4 non-halo clusters: A576, A1795, A478, A2204
Chandra: Bullet Cluster Surface Brightness and Temperature (kt) maps: Mean kt is ~ 14 kev!
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 0657-56 (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 10 16 ergs s 1 cm 2 arcsec 2 are shown in this map. Each spatial region has 10 4 net counts in the 0.6 7.0 kevchandraband.
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 0657-56
Bullet Cluster: NuStar (266 ks): Wik et al. 2014 Very hot kt ~ 15.3 kev, and no evidence for a NT component above 20 kev
s 1 ) 7 10 Fermi era: Ackermann et al. 2010 33 clusters from 18 months of data F > 0.1 GeV ( ph cm 2 s 1 ) F > 0.1 GeV ( ph cm 2 8 10 9 10 10 10 7 10 8 10 9 10 10 10 3C129 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 2 7 10 8 10 9 10 10 10 Donnert et al. 2010 EGRET 0.95 CL LAT 0.95 CL MACSJ0717 NGC5044 NGC5846 NGC4636 NGC5813 Norma Ophiuchus Perseus RXJ1347 Triangulum Virgo
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
Best Targets for Astrosat SXT+LAXPC (& ASTRO- H) 1. The brightest radio relic: The NW relic of Abell 3667 2. The radio halo in the Coma Cluster
THANKS!