Relativistic Flows in Astrophysics

The topic of this book is the study of relativistic outflows such as those seen in gamma-ray bursts, microquasars and active galactic nuclei. The book starts with lectures on physical processes relevant to all astrophysical systems exhibiting relativistic flows. Further lectures concentrate on more specific aspects such as various mechanisms for particle acceleration and radiation from relativistically moving sources. This volume will thus be of interest to postgraduate students and nonspecialist researchers as a tutorial introduction to this subject as well as for the experienced researcher looking for a modern source of reference.

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1. 1 Schematic Picture of AGN Some galaxies are known to emit radiation with extremely high luminosities from a rather small volume in the ??ray, X-ray and UV continuum. Such active cores are the so-called Active Galactic Nuclei (AGN) and the radiation is commonly believed to be a result of gravitational energy released by matter spiraling around 9 a supermassive central black hole of about 10 M (see Fig. 1). Though the central engine which produces the enormous observed activity cannot be resolved observationally, a standard picture of an AGN has gradually emerged to explain the richness of the radiation spectra: - an accretion disk with radius from about 2 to 100 gravitational radii, R , g feeding the central black hole and emitting mainly in the UV and soft X-rays; - the broad line optically emitting clouds (BLR), which seem to be absent in 3 some sources (e. g. FRI, see hereafter) and extend up to a few 10 R from g the center.