Lecture 20 Accretion spectrum Gravitational redshift Iron Kα line Spinning black holes

Spectrum produced by standard geometrically thin, optically thick accretion disk

Models of accretion spectra for various central masses and accretion rates

Effective potential in Schwarzschild metric

Orbits in a Schwarzschild metric

X-ray spectral features

Formation of Kα doublet

Monte Carlo simulation of a reflection spectrum from a slab of uniform density neutral matter with solar abundances Main components of the X-ray Spectrum of an unobscured Accreting BH

Photon shifts Photons from the accretion disc are redshifted because of the Gravitational redshift and the Doppler transverse effect, and blueshifted /redshifted by the Doppler effect when the matter is approaching/receding

Doppler boosting The quantity Iυ/υ3 is a Lorentz invariant Therefore, the blueshifted radiation is brighter (Doppler boosting), the redshifted one is fainter

X-ray spectral features The abovementioned SR and GR effects modify the line profile in a characteristic and well-recognizable way (Fabian et al. 2000)

Relationship between ISCO radius and spin Schwarzschild BH Maximal Kerr BH

Dependence of the line profile on the Emissivity profile of the disk: R^-q The steeper the emissivity, the broader The line profile because more emphasis Is given to the innermost radii, where the GR effects are strongest Dependence of the line profile on the observer inclination

MCG-6-30-15 (37 Mpc) a>0 !!! ASCA (Tanaka et al. 1995)

XMM-Newton spectrum of Seyfert 1 MCG-6-30-15 Fabian et al. 2002

BIBLIOGRAPHY A.C. Fabian, K. Iwasawa, C.S. Reynolds, & A.J. Young 2000 Broad iron lines in Active Galactic Nuclei, PASP, 112, 1145 A.C. Fabian & G. Miniutti 2008 The X-ray spectra of accreting Kerr black holes In: The Kerr Spacetime: Rotating Black Holes in General Relativity Eds. D.L. Wiltshire, M. Visser, S. M. Scott (CUP) (astro-ph/0507409) J. Frank, A.R. King, D.J. Raine 1985 Accretion Power in Astrophysics Cambridge University Press Ghisellini 2013 Radiative Processes in High Energy Astrophysics Lecture Notes in Physics, Vol. 873 Springer C.S. Reynolds & M.A. Nowak 2003 Fluorescent iron lines as a probe of astrophysical black hole systems Physics Reports, 377, 389 (astro-ph/0212065) G.E. Romero & G.S. Vila 2014 Introduction to Black Hole Astrophysics Lecture Notes in Physics Vol. 876