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Zoom and whirl: Eccentric equatorial orbits around spinning black holes and their evolution under gravitational radiation reaction

Glampedakis, Kostas and Kennefick, Daniel (2002) Zoom and whirl: Eccentric equatorial orbits around spinning black holes and their evolution under gravitational radiation reaction. Physical Review D, 66 (4). Art. No. 044002. ISSN 2470-0010. doi:10.1103/PhysRevD.66.044002.

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We study eccentric equatorial orbits of a test-body around a Kerr black hole under the influence of gravitational radiation reaction. We have adopted a well established two-step approach: assuming that the particle is moving along a geodesic (justifiable as long as the orbital evolution is adiabatic) we calculate numerically the fluxes of energy and angular momentum radiated to infinity and to the black hole horizon, via the Teukolsky-Sasaki-Nakamura formalism. We can then infer the rate of change of orbital energy and angular momentum and thus the evolution of the orbit. The orbits are fully described by a semilatus rectum p and an eccentricity e. We find that while, during the inspiral, e decreases until shortly before the orbit reaches the separatrix of stable bound orbits [which is defined by p(s)(e)], in many astrophysically relevant cases the eccentricity will still be significant in the last stages of the inspiral. In addition, when a critical value p(crit)(e) is reached, the eccentricity begins to increase as a result of continued radiation induced inspiral. The two values p(s), p(crit) (for given e) move closer to each other, in coordinate terms, as the black hole spin is increased, as they do also for fixed spin and increasing eccentricity. Of particular interest are moderate and high eccentricity orbits around rapidly spinning black holes, with p(e)approximate top(s)(e). We call these "zoom-whirl" orbits, because of their characteristic behavior involving several revolutions around the central body near periastron. Gravitational waveforms produced by such orbits are calculated and shown to have a very particular signature. Such signals may well prove of considerable astrophysical importance for the future Laser Interferometer Space Antenna detector.

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Additional Information:©2002 The American Physical Society. Received 28 March 2002; published 15 August 2002. The authors wish to thank Scott Hughes, Sterl Phinney, B.S. Sathyaprakash, Wolfram Schmidt and Lee Lindblom for very useful discussions and comments. In addition K.G. thanks the State Scholarships Foundation of Greece for financial support. He would also like to acknowledge support from PPARC grant PPA/G/0/1999/0214. D.K. thanks the Astronomy Department of Oxford University for the generous use of their facilities and their unfailingly warm hospitality which greatly aided this research. In particular he would like to thank Julia Kennefick and Gavin Dalton. He would also like to acknowledge support from NSF grant PHY-0099568, and the help of the Physics and Astronomy Department at Cardiff University.
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4327
Deposited By: Tony Diaz
Deposited On:17 Aug 2006
Last Modified:08 Nov 2021 20:16

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