8th HEAD Meeting, 8-11 September, 2004
Session 20 Black Hole Binaries and Intermediate Mass Black Holes
Oral, Thursday, September 9, 2004, 2:00-3:38pm

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[20.05] Super-Keplerian Oscillation Frequencies in Numerical Models of Accretion Disks

S. A. Mao, J. A. Milsom, D. Psaltis (University of Arizona -Department of Physics)

The masses, spins, and sizes of the emitting regions of accreting neutron stars and black holes have often been constrained using the assumption that super-Keplerian frequencies cannot be observed from any radius of their accretion disks. This is equivalent to assuming that the frequency of the lowest order, linear, hydrodynamic mode at any radius has to be smaller than the local Keplerian frequency. We investigate the validity of this assumption using a systematic numerical study of vertically integrated, axisymmetric, viscous accretion disks around non-rotating black holes. In these simulations, we find radial oscillations which are often super-Kelperian. Depending upon the black-hole mass,the accretion rate, and the viscosity, oscillations primarily at the fundamental, second, or even fourth harmonic of the Keplerian frequency are excited at various radii. We discuss the implications of our results for the phenomenological constraints imposed on compact object properties by the observation of high-frequency quasi-periodic oscillations.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.