Observational appearance of strong gravity in X-rays
Compact object Companion star (5000 K)
Schwarzschild radius Schwarzschild metric R s 2GM Schwarzschild radius (= 2.95 km for 1М ) c 2
Accretion Black holes can be seen via their influence on nearby objects Accretion gradual motion of matter towards gravitating object Where the matter comes from? interstellar from companion star Mass accretion rate and the luminosity
Accretion luminosity 1 GMcM 2R c 2 2 L ~ ~ Mc Mc R c R s 2GM Rs - Schwarzschildradius(= 3 km for 1M 2 c 2R Rs c 1 - accretionefficiency sun ) M ~ 10 L x ~ 10-8 38 Msun/yr erg/s ~ 0.1, R c ~ 5R s (~ 15km for 1M sun )
Why X-rays? R ~ 5 R S = 4 R L x ~ T 2 4 s ~ 15 - emitting area S T ~ 1.6 10 7 (Stefan - Boltzman law) M M M M Sun Sun 1/2 km K ~ 1-2 M M Sun 1/2 kev ~ 1 2 kev for NS ~ 0.3 0.7 kev for BH
Black body emission Rayleigh-Jeans law
Stefan-Boltzman law
Black body normalization => size of the emitter
Scheme of BH with accreton disk
Non rotating BH Rotating BH Inner disk radius -> BH parameters
Radius of innermost stable orbit around rotating BH
~kt ~Rin Inner disk radius?
Problem 1: Brightness distribution The simplest case T~ R -3/4
RJ law The simplest case
Shakura, Sunyaev 1973
Norman, Krolik, Schnittman et al.
Disk surface brightness in simulations Beckwith et al. 2008
Problem 2: Disk atmosphere (opacity and Comptonization)
Opacity dependence on energy/wavelength
Comptonization Одно рассеяние: ~ E e m e c 2 ~ 4kT e m e c 2 если гладкий спектр / 1 Степенной закон между ~kt seed and ~3kT e Тепловой завал на @3kT e ~ + 4kT e m e c 2 h m e c 2
Suleimanov et al. In order to have the outgoing flux one need to have gradient of energy density, gradient of temperature Atmosphere
Suleimanov et al. Spectral kt c ~1.7kT distortion
Lum-Tdisk dependence and color correction Davis et al. 2006
Problem 3 (small) Light bending
Black hole parameters from properties of fluorescent emission lines?
Reflection from rapidly rotating accretion disk
Relativistic line in AGN MCG-6-30-15? ASCA (1995) Tanaka et al. 1995
MCG-6-30-15 XMM (2002)
Interpretation problem: line of sight absorption?
Problems 4. Characteristics of instruments
Energy response of instruments X-rays are measured in counts(c) at energy channels (h) h- energy channel (from pulse height ) M model of true emission of the source A(E) effective area of the instrument as a function of energy R(E,h) redistribution matrix of photons into channels
Finite energy resolution
Even worse in early experiments:
Processes in detectors
Counts Photopeak Ka photons Compton effect
Non-diagonal elements redistribution matrix of Si CCD
1995 Proportional Counters response 1979 Limited by electron counts Escape peaks
CCD camera SIS/ASCA (1993-2001)
CHANDRA/ACIS-I (1999- )
Effective area of instruments
Calibration issues Schellenberger et al. 2014 XMM-CHANDRA cross-calibration
XMM-CHANDRA-SUZAKU cross-calibration with blazar Ishida et al. 2011
XMM-CHANDRA-SUZAKU-SWIFT-RXTE-INTEGRAL cross-calibration with supernova remnant Tsujimoto et al. 2010
Ice absorption on SSS detector of EINSTEIN
Accuracy of effective areas of detectors CHANDRA ACIS-S Effective area Drops at energies below 2 kev due to CCD surface contamination
Spatial distribution of abs.contamination (SUZAKU)
CHANDRA/ACIS
Charge transfer inefficiency
Catechism of X-ray astronomer 1. Before making strong claims one should pay attention to calibration issues!
E E Problem pile-up dt(pile-up) 2E 2 photons with some energies might look as one photon with larger energy
Or might even be rejected after post processing due to energy higher than high threshold
Even in gas counters pile up effect is present PCA spectrometer (dt~10-5 sec) For CCD dt~0.1-1 sec!
Pile-up problems of XMM
MOS PN comparison EPIC-PN CCD camera less affected by pile up
Fluorescent lines in emission of NS binaries Ng et al. 2011
With wrong Cackett et al. correction With correction Dias-Trigo et al.
Example of file with events
EXAMPLE of real event file of X-ray detector
Next step- microcalorimeter Astro-H(Japan) 2015?
Maximum likelihood