Reprocessed emission from warped accretion discs with application to X-ray iron line profiles |
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Authors: | Sean A. Hartnoll Eric G. Blackman |
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Affiliation: | Theoretical Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA;St John's College, University of Cambridge, Cambridge CB2 1TP;Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA |
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Abstract: | Fluorescent iron line profiles currently provide the best diagnostic for engine geometries of active galactic nuclei (AGN). Here we construct a method for calculating the relativistic iron line profile from an arbitrarily warped accretion disc, illuminated from above and below by hard X-ray sources. This substantially generalizes previous calculations of reprocessing by accretion discs by including non-axisymmetric effects. We include a relativistic treatment of shadowing by ray-tracing photon paths along Schwarzschild geodesics. We apply this method to two classes of warped discs, and generate a selection of resulting line profiles. New profile features include a time-varying line profile if the warp precesses about the disc, profile differences between 'twisted' and 'twist-free' warps and the possibility of steeper red and softer blue fall-offs than for flat discs. We discuss some qualitative implications of the line profiles in the context of Type I and II Seyfert AGN and other sources. |
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Keywords: | accretion, accretion discs line: formation line: profiles galaxies: active galaxies: Seyfert X-rays: galaxies |
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