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Astron. Astrophys. 362, 1-8 (2000)

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Comptonization in an accretion disk illuminated by protons

B. Deufel and H.C. Spruit

Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85740 Garching, Germany

Received 17 February 2000 / Accepted 6 June 2000


We compute the X-ray spectrum from a cool, optically thick, geometrically thin accretion disk embedded in a hot ion supported torus (or ADAF). Most of the gravitational power is assumed to be dissipated in the torus, where the protons are near their local virial temperature. The protons are slowed down in the accretion disk via Coulomb interactions, producing a hot surface layer with an optical thickness [FORMULA]1-2. The heating of this layer is balanced by cooling through Comptonization of soft photons. The soft photons are produced by the reprocessing (treated in an approximate way) of hard photons penetrating into the cool disk. Solving the energy balance problem of the heated layer together with the Comptonization by a Monte-Carlo simulation, we find X-ray spectra reminiscent of observed spectra of AGN and black hole candidates in their hard states.

Key words: accretion, accretion disks – black hole physics – radiative transfer – scattering – X-rays: galaxies – X-rays: stars

Send offprint requests to: bed@mpa-garching.mpg.de

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© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100