X-ray spectroscopy of active galaxies

The X-ray reflection features of irradiated accretion disks around black holes enable us to probe the effects of strong gravity and learn the black-hole properties. We investigate the reflection signs, i.e. the iron K-line and the Comptonized hump, which arise by reprocessing of radiation on the surface of an accretion disc, and how they are affected by the spin of a rotating black hole.

We have developed a new ray-tracing routine that enhances capabilities to model the emission line profiles from black-hole accretion discs. The new routine, "ky", cooperates with XSPEC. It is supposed to be more accurate and versatile than laor (Laor 1991), and faster than kerrspec (Martocchia et al. 2000). Among other features, ky allows to fit various parameters such as black hole angular momentum, observer inclination, an accretion disc size, etc. It also allows to change the grid resolution and, hence, to control accuracy and computational speed. There is an option to explore time variable sources.

Currently, the routine implements tabulated Kerr metric functions in equatorial plane. A set of data files has been prepared that contains information about light rays originating in a thin disc and reaching a distant observer. The files can be used to compute observed spectra of a Keplerian accretion disc around a rotating (Kerr) black hole. This page provides some technical details about ray-tracing computations that have been performed to create the output data. A conference poster (Computational fluid dynamics in astrophysics, September 2003, University of Leicester, UK) illustrates the basic features and capabilities of the code. A detailed description of the new XSPEC subroutine is available in our papers. Read more...


  • Dovciak M., Karas V., Yaqoob T., 2004, ApJS, 153, 205 [ads]
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