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

By K. Glampedakis, D. Kennefick. 2002

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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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3c8e0d831941484dc3871d7e97f7688f066e7079

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Citations in the corpus

Two timescale analysis of extreme mass ratio inspirals in Kerr. I. Orbital Motion (2008, methodology): “Black hole perturbation theory – first order: There is a long history of using first order perturbation theory [3] to compute gravitational waveforms from particles in geodesic orbits around black holes [33, 34, 35, 36].”
Gravitational wave snapshots of generic extreme mass ratio inspirals (2005, methodology): “Shibata has since reported that after improving his code, he now agrees with Glampedakis and Kennefick to much greater accuracy [69].”
Physics, Astrophysics and Cosmology with Gravitational Waves (2009, background): “The emitted gravitational radiation [317, 179, 178, 67, 171, 57] would consist of a very long wave train that carries information about the nearly geodesic trajectory of the test body, thereby providing a very clean probe to survey the spacetime geometry of the central object (which could be a Kerr ”