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M. Sobolewska (CfA/CAMK), A. Siemiginowska (CfA), P. Zycki (CAMK)
Two families of models are currently considered to describe an accretion flow into black holes and production of the observed X-ray radiation: (1) a standard cold accretion disk with a hot corona above it, and (2) an outer truncated accretion disk with an inner hot semi-spherical flow. We present computations of X-ray spectra based on the model developed by Rozanska & Czerny (2000). In this approach, an evaporation of the disk material due to the heat conducted from the corona is responsible for the radial and/or vertical division of the accreting material into two phases. For low accretion rates the model predicts the radius of a complete disk evaporation into a hot central spherical flow. For higher values of the accretion rate the geometry remains plane-parallel; the disk and the hot corona extend to the last stable orbit. The parameters of the model are: the black hole mass, accretion rate, and disk viscosity. We compare the computed spectra with those presented by Janiuk & Czerny (2000) and Janiuk, Zycki & Czerny (2000), where the criterion of thermal instability was used to determine the vertical division of the accreting medium.
Our computations can be used to test the geometry of accretion in active galactic nuclei, as well as in galactic black hole X-ray binaries. Here we present the application of our model to a sample of high redshift quasars.
References:
Janiuk A. & Czerny B., 2000, New Astronomy, 5, 7
Janiuk A., Czerny B., & Zycki P., 2000, MNRAS, 314, 364
Rozanska A. & Czerny B., 2000, A&A, 360, 1170
Acknowledgments:
This research is funded in part by NASA contract NAS8-39073. Partial support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number GO1-2117B and GO2-3148A issued by the Chandra X-Ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-39073. MS acknowledges support from the Smithsonian Institution Pre-doctoral fellowship program.
Bulletin of the American Astronomical Society,
35#2
© 2003. The American Astronomical Soceity.