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Disk-Corona Models and X-Ray Emission from Seyfert Galaxies

Published online by Cambridge University Press:  12 April 2016

Laura Maraschi  and
Francesco Haardt
Laura Maraschi
Affiliation:
Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
Francesco Haardt
Affiliation:
Department of Astronomy & Astrophysics, Institute of Theoretical Physics, Göteborg University & Chalmers University of Technology, 412 96 Göteborg, Sweden

Abstract

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The current status of understanding of the X-ray emission from Seyfert galaxies involves Comptonization of soft photons by hot subrelativistic electrons. After briefly reviewing the early theoretical basis for the presence of hot optically thin plasma in or around accretion disks and the key observations that led to develop the presently popular model of an accretion disk with a hot corona, we summarize recent progress in accretion models that take into account energy dissipation and/or angular momentum transport in the corona. Finally, adopting the simple scheme of a homogeneous plane parallel corona, we discuss in detail the dependence of the X-ray spectrum on the coronal parameters. Despite the strong coupling between optical depth and temperature which determines a spectral shape insensitive to their precise values, moderate spectral changes are possible. The spectral variability patterns can be used as diagnostics for coronal physics and should allow to determine whether the optical depth of the corona is dominated by e+e− pairs.

Type
Part 3. Fundamental Physical Processes
Information
International Astronomical Union Colloquium , Volume 163: Accretion Phenomena and Related Outflows , 1997 , pp. 101 - 112
Copyright
Copyright © Astronomical Society of the Pacific 1997

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