Epicyclic Oscillations of Fluid Bodies: Newtonian Nonslender Torus

Omer M. Blaes; Eva Sramkova; Marek A. Abramowicz; Wlodek Kluzniak; Ulf Torkelsson

doi:10.1086/519782

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arXiv · 0706.4483

Epicyclic Oscillations of Fluid Bodies: Newtonian Nonslender Torus

Omer M. Blaes·Eva Sramkova·Marek A. Abramowicz·Wlodek Kluzniak·Ulf Torkelsson

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Abstract

We study epicyclic oscillations of fluid tori around black holes (in the Paczynski-Wiita potential) and derive exact analytic expressions for their radial and vertical eigenfrequencies nu_r and nu_z to second-order accuracy in the width of the torus. We prove that pressure effects make the eigenfrequencies smaller than those for free particles. However, the particular ratio nu_z/nu_r=3/2, which is important for the theory of high-frequency quasi-periodic oscillations (QPOs), occurs when the fluid tori epicyclic frequencies nu_r and nu_z are about 15% higher than the ones corresponding to free particles. Our results therefore suggest that previous estimates of black hole spins from QPOs have produced values that are too high.

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Omer M. Blaes, Eva Sramkova, Marek A. Abramowicz, Wlodek Kluzniak, Ulf Torkelsson. 2007-06-29. Epicyclic Oscillations of Fluid Bodies: Newtonian Nonslender Torus. https://doi.org/10.1086/519782

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