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Lindblad resonance torques in relativistic discs – II. Computation of resonance strengths

Hirata, Christopher M. (2011) Lindblad resonance torques in relativistic discs – II. Computation of resonance strengths. Monthly Notices of the Royal Astronomical Society, 414 (4). pp. 3212-3230. ISSN 0035-8711.

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We present a fully relativistic computation of the torques due to Lindblad resonances from perturbers on circular, equatorial orbits on discs around Schwarzschild and Kerr black holes. The computation proceeds by establishing a relation between the Lindblad torques and the gravitational waveforms emitted by the perturber and a test particle in a slightly eccentric orbit at the radius of the Lindblad resonance. We show that our result reduces to the usual formula when taking the non-relativistic limit. Discs around a black hole possess an m = 1 inner Lindblad resonance (ILR) with no Newtonian–Keplerian analogue; however, its strength is very weak even in the moderately relativistic regime (r/M ~ few tens), which is in part due to the partial cancellation of the two leading contributions to the resonant amplitude (the gravitoelectric octupole and gravitomagnetic quadrupole). For equatorial orbits around Kerr black holes, we find that the m = 1 ILR strength is enhanced for retrograde spins and suppressed for prograde spins. We also find that the torque associated with the m ≥ 2 ILRs is enhanced relative to the non-relativistic case; the enhancement is a factor of 2 for the Schwarzschild hole even when the perturber is at a radius of 25M.

Item Type:Article
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Hirata, Christopher M.0000-0002-2951-4932
Additional Information:© 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS. Accepted 2011 February 28. Received 2011 February 24; in original form 2010 October 10. Article first published online: 2 May 2011. CMH thanks Tanja Hinderer, Mike Kesden and Dave Tsang for numerous helpful conversations. CMH is supported by the US Department of Energy under contract DE-FG03-02-ER40701, the National Science Foundation under contract AST-0807337 and the Alfred P. Sloan Foundation.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-02-ER40701
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:accretion, accretion discs; black hole physics; relativistic processes
Issue or Number:4
Record Number:CaltechAUTHORS:20110815-103000012
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24852
Deposited By: Ruth Sustaita
Deposited On:15 Aug 2011 18:07
Last Modified:03 Oct 2019 03:00

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