Energetic Photon Spectra as Probes of the Process of Particle Acceleration in Accretion Flows Around Black Holes

Abstract

Most of the powerful astronomical objects discovered over the past three decades appear to be energised by the accretion of matter on to condensed massive bodies residing in their centres. X-ray binaries, active galactic nuclei, extragalactic double radio sources displaying relativistic jets and other such interesting phenomena are some examples for which an important part of the gravitational energy associated with the inflow of matter is radiated away as non-thermal particles and quanta. Excellent overviews of the relevant astronomical literature and of the physical processes related with accretion flows on to black holes are provided by Rees [1], Begelman et al.[2] and by Frank et al. [3]. In recent years the evidence for the existence of both supermassive black holes (M BH ~ 106 — 108 M ⊙) and stellar mass black holes is accumulating rapidly [4–7].