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Astron. Astrophys. 339, 87-94 (1998)


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Radiation feedback in hot accretion-disk corona models
and application to GX 339-4

M. Böttcher , E.P. Liang and I.A. Smith

Rice University, Space Physics and Astronomy Department, MS 108, 6100 S. Main Street, Houston, TX 77005-1892, USA

Received 29 June 1998 / Accepted 18 August 1998

Abstract

We present a detailed study of the observable effects of photoionization and Comptonization of line and continuum radiation from a cold accretion disk with a thin, warm, photoionized transition layer in the framework of self-consistent accretion-disk corona models for Galactic black-hole candidates. We use an iterative method to treat the non-linear radiation feedback between the transition layer and the hot corona numerically using a Monte-Carlo Comptonization code in combination with the photoionization and line transfer code XSTAR. The subset of the parameter space allowed in self-consistent accretion-disk corona systems on energetic grounds is explored, checking for the emergence of emission lines and/or absorption edges, with special emphasis on the spectral range below a few keV, where such features might become observable with the advent of the AXAF satellite, and investigating the significance of the Compton reflection hump. Comparing our model calculations to the broadband spectrum of GX 339-4, we find good agreement with the observed spectral features, in particular the absence of a Compton reflection component. We discuss how the future detection of the predicted features at lower energies can be used to constrain parameters.

Key words: X-rays: stars – accretion, accretion disks – line: formation – radiative transfer – radiation mechanisms: thermal

Send offprint requests to: M. Böttcher

© European Southern Observatory (ESO) 1998

Online publication: September 30, 1998

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