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M. Boettcher (Ohio University), E. P. Liang (Rice University)
We discuss results of time-dependent numerical simulations of radiation-transfer and electron-dynamics problems in 2 spatial dimensions, obtained with our coupled Monte-Carlo / Fokker-Planck code. We choose a generic accretion-disk corona model setup resulting in a time-averaged photon spectrum similar to GRS 1915+105 in its high/soft state. On the basis of this setup, a parameter study of a few fundamentally different flaring scenarios has been performed. Our results indicate several important differences to previous work in which a similar approach in 1-D geometries was used. If rapid flaring of X-ray binaries in such a situation is initiated by flares in a limited annulus of the underlying accretion disk, we find the previously reported spectral pivoting of the X-ray spectrum around ~20 keV to be much less pronounced or even absent in the 2-D simulations. Depending on the specific model assumptions for individual flares, the disk-flaring scenario may produce both hard and soft lags, and a slight hardening of the high-frequency power spectra with increasing photon energy. Alternatively, if flaring originates in the corona, we find no significant energy dependence of the power spectra in our test cases, and the variability at energies around 10 keV seems to lead variations at other photon energies. More recent results pertaining to alternative accretion-flow geometries will be reported at the meeting.
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Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.