Open AccessA quasi‐spherical inner accretion flow in Seyfert galaxies?
Author(s) -
Malzac Julien
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04564.x
Subject(s) - physics , astrophysics , accretion (finance) , amplitude , galaxy , reflection (computer programming) , cooling flow , flux (metallurgy) , plasma , dissipation , active galactic nucleus , spectral line , astronomy , optics , materials science , quantum mechanics , computer science , metallurgy , thermodynamics , programming language
We study a phenomenological model for the continuum emission of Seyfert galaxies. In this quasi‐spherical accretion scenario, the central X‐ray source is constituted of a hot spherical plasma region surrounded by spherically distributed cold dense clouds. The cold material is radiatively coupled with the hot thermal plasma. Assuming energy balance, we compute the hard X‐ray spectral slope Γ and the reflection amplitude R . This simple model enables us to reproduce both the range of observed hard X‐ray spectral slopes and the reflection amplitude R . It also predicts a correlation between R and Γ that is very close to what is observed. Most of the observed spectral variations from source to source would be caused by differences in the cloud covering fraction. If some internal dissipation process is active in the cold clouds, darkening effects may provide a simple explanation for the observed distributions of reflection amplitudes, spectral slopes and ultraviolet to X‐ray flux ratios.