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D.R. Ballantyne (CITA), N.J. Turner (JPL), A.J. Young (MIT)
One of the principal scientific objectives of the upcoming Constellation-X mission is to attempt to map the inner regions of accretion disks around black holes in Seyfert galaxies by reverberation mapping of the Fe K fluorescence line. Here, we show that density inhomogeneities in the disk atmosphere resulting from the photon bubble instability can cause rapid changes in the X-ray reflection features, even when the illuminating flux is constant. Using a numerical simulation of the evolution of the photon bubble instability, the Fe K and O VIII Ly\alpha lines are found to vary on timescales as short as a few one-hundredths of an orbital time. In response to the changes in accretion disk structure, the Fe K equivalent width shows variations as large as ~100 eV. The magnitude and direction (positive or negative) of the changes depends on the ionization state of the atmosphere. The largest changes are found when the disk is moderately ionized. This effect provides a natural explanation for some observed instances of short timescale Fe K variability which was uncorrelated with the continuum.
The author(s) of this abstract have provided an email address for comments about the abstract: ballantyne@cita.utoronto.ca
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.