Epicyclic Oscillations of Fluid Bodies: Newtonian Nonslender Torus

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 eigenfrequendes [unk] and v2 to second-order accuracy in the width of the torus. We prove that pressure effects make the eigenfreque...

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Veröffentlicht in:The Astrophysical journal 2007-08, Vol.665 (1), p.642-653
Hauptverfasser: Blaes, Omer M, Šrámková, Eva, Abramowicz, Marek A, Kluźniak, Włodek, Torkelsson, Ulf
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Sprache:eng
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Zusammenfassung: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 eigenfrequendes [unk] and v2 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 v2/ [unk] = 3/2, which is important for the theory of high-frequency quasi-periodic oscillations (QPOs), occurs when the fluid tori epicyclic frequencies [unk] and v2 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.
ISSN:0004-637X
1538-4357
DOI:10.1086/519782