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M. Ortega-Rodriguez, A. S. Silbergleit, R. V. Wagoner (Stanford Univ.)
We investigate two types of modes of oscillation trapped in accretion disks, in part by the strong-field gravitational properties of a black hole (or a compact, weakly-magnetized neutron star). The first type are the c(`corrugation')--modes, nearly incompressible perturbations of the inner disk. The fundamental c--modes have eigenfrequencies (ordered by radial mode number) which correspond to the Lense--Thirring frequency, evaluated at the outer trapping radius of the mode, in the slow rotation limit. This trapping radius is a decreasing function of the black hole angular momentum, so a significant portion of the disk is modulated only for slowly rotating black holes. The eigenfrequencies are thus strongly increasing functions of black hole angular momentum. The dependence of the eigenfrequencies on the speed of sound (or the luminosity) within the disk is weak, except for slowly rotating black holes. The second type are the p--modes, similar to the pressure (acoustic) modes of stars. We discuss properties of the three classes of p--modes, determined by their location within the accretion disk: inner, outer, and full-disk. This work was supported by NASA grants NAS 8-39225 and NAG 5-3102.
The author(s) of this abstract have provided an email address for comments about the abstract: manuel@leland.stanford.edu