An analytic steady state solution to the Fokker-Planck equation for Compton scattering in a spherical inflow, where internal monochromatic photons scatter off thermal nonrelativistic electrons undergoing radial bulk motion, is derived. It is found that photon advection by electrons yields an overall reduction in the intensity of the emerging spectrum with increasing velocity. In the case of soft photons emitted close to the trapping surface and small scattering optical depths, the outgoing spectrum is a power law with a slope that depends only on a plasma parameter proportional to the ratio of the Compton time to the infall time. At large values of the optical depth, the spectra show a depletion of high-energy photons being preferentially convected inward and ultimately trapped by the inflowing electrons. If soft radiation is emitted far from the trapping surface, the computed spectra significantly deviate from a power law. The results of these calculations are relevant to the case of supercritical spherical accretion onto black holes.

Colpi, M. (1988). Multiple Compton scattering by thermal electrons in a spherical inflow - The effects of bulk motion. THE ASTROPHYSICAL JOURNAL, 326, 223 [10.1086/166083].

Multiple Compton scattering by thermal electrons in a spherical inflow - The effects of bulk motion

COLPI, MONICA
1988

Abstract

An analytic steady state solution to the Fokker-Planck equation for Compton scattering in a spherical inflow, where internal monochromatic photons scatter off thermal nonrelativistic electrons undergoing radial bulk motion, is derived. It is found that photon advection by electrons yields an overall reduction in the intensity of the emerging spectrum with increasing velocity. In the case of soft photons emitted close to the trapping surface and small scattering optical depths, the outgoing spectrum is a power law with a slope that depends only on a plasma parameter proportional to the ratio of the Compton time to the infall time. At large values of the optical depth, the spectra show a depletion of high-energy photons being preferentially convected inward and ultimately trapped by the inflowing electrons. If soft radiation is emitted far from the trapping surface, the computed spectra significantly deviate from a power law. The results of these calculations are relevant to the case of supercritical spherical accretion onto black holes.
Articolo in rivista - Articolo scientifico
black holes; radiative mechanisms; radiative transfer
English
223
Colpi, M. (1988). Multiple Compton scattering by thermal electrons in a spherical inflow - The effects of bulk motion. THE ASTROPHYSICAL JOURNAL, 326, 223 [10.1086/166083].
Colpi, M
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10281/37924
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