The current routine implements tabulated Kerr metric 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 basic features and capabilities of the code. Further, a more detailed description of the new XSPEC subroutine is available.
First, we had to create data tables that characterize light-ray propeties (so that geodesics do not have to be integrated each time a spectrum is computed). Some assumptions about the source emissivity must be adopted at this point: e.g., a planar disc near a black hole. Given a set of data tables, one can use stand-alone codes (without any link to XSPEC) to compute predicted spectra. This approach is convenient to test the data tables.