A cloud model of active galactic nuclei: the iron Kα line diagnostics |
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Authors: | V. Karas B. Czerny A. Abrassart M. A. Abramowicz |
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Affiliation: | Astronomical Institute, Charles University Prague, V Holešovickách 2, CZ-180 00 Praha, Czech Republic;Nicolaus Copernicus Astronomical Center, Bartycka 18, PL-00 716 Warsaw, Poland;DAEC, Observatoire de Paris, Section de Meudon, F-92 195 Meudon, France;Institute for Theoretical Physics, Göteborg University and Chalmers University of Technology, S–412 96 Göteborg, Sweden |
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Abstract: | The origin and the profile of the iron K α line from active galactic nuclei are studied. The model with a quasi-spherical distribution of clouds around a compact galactic nucleus is explored, in which the intrinsic spectral feature around 6–7 keV is substantially affected by Comptonization of primary X-rays. The predicted spectral profiles are influenced mainly by the motion of the clouds in the strong gravitational field of the centre, and by the orientation of the source with respect to the observer. The case of the Seyfert galaxy MCG–6-30-15 is examined in more detail and free parameters of the model are determined. A robust result is obtained: acceptable fits to the observed profile correspond to a spherical distribution of the clouds with strong self-obscuration effects and with a rather high value of ionization parameter. This is a different situation from that considered in the model of a cold illuminated disc. Nevertheless, geometrically flat (disc-type) configurations are not rejected. |
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Keywords: | accretion, accretion discs galaxies: active galaxies: individual: MCG–6-30-15 galaxies: Seyfert X-rays: galaxies X-rays: stars |
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