1995/08/07 by Ramesh Narayan, Narayan, Ramesh
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9508031
20 pages, 3 figures included, compressed uuencoded Postscript, Review talk at the conference on "Some Unsolved Problems in Astrophysics," Princeton, April 27-29, 1995. To appear in the Proceedings to be published by Princeton Univ. Press (editors, J. N. Bahcall & J. P. Ostriker)
Most accreting black holes emit a substantial fraction of their luminosity in hard X-rays/soft γ-rays of up to ∼\rm few×100 keV. The observations suggest that the radiating gas is very hot, T>109 K, and optically thin. Theoretical attempts to explain the observations are reviewed and unresolved issues are highlighted.