Evolution of circular, nonequatorial orbits of Kerr black holes due to gravitational-wave emission. II. Inspiral trajectories and gravitational waveforms

By S. Hughes. 2000

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The inspiral of a ``small'' $(\ensuremath{\mu}\ensuremath{\sim}1\ensuremath{-}100{M}_{\ensuremath{\bigodot}})$ compact body into a ``large'' $(M\ensuremath{\sim}{10}^{5\ensuremath{-}7}{M}_{\ensuremath{\bigodot}})$ black hole is a key source of gravitational radiation for the space-based gravitational-wave observatory LISA. The waves from such inspirals will probe the extreme strong-field nature of the Kerr metric. In this paper, I investigate the properties of a restricted family of such inspirals (the inspiral of circular, inclined orbits) with an eye toward understanding observable properties of the gravitational waves that they generate. Using results previously presented to calculate the effects of radiation reaction, I assemble the inspiral trajectories (assuming that radiation reacts adiabatically, so that over short time scales the trajectory is approximately geodesic) and calculate the wave generated as the compact body spirals in. I do this analysis for several black hole spins, sampling a range that should be indicative of what spins we will encounter in nature. The spin has a very strong impact on the waveform. In particular, when the hole rotates very rapidly, tidal coupling between the inspiraling body and the event horizon has a very strong influence on the inspiral time scale, which in turn has a big impact on the gravitational wave phasing. The gravitational waves themselves are very usefully described as ``multi-voice chirps'': the wave is a sum of ``voices,'' each corresponding to a different harmonic of the fundamental orbital frequencies. Each voice has a rather simple phase evolution. Searching for extreme mass ratio inspirals voice-by-voice may be more effective than searching for the summed waveform all at once.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/2f7370799ec78f5c85e4a14e8e44f78e6d00488d

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Citations in the corpus

Black Hole Spin Evolution (2003, background): “The inspiral may be regarded as progressing through a series of nearly circular orbits of fixed inclination (Hughes 2001).”
Global General Relativistic Magnetohydrodynamic Simulation of a Tilted Black Hole Accretion Disk (2007, methodology): “Following Hughes (2001) we can eliminate Q in favor of the inclination i defined as cos i ¼ Lz Lz þ Qð Þ1=2 : ð23Þ Figure 5 illustrates this dependence for a few selected cases of a.”