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Published July 15, 2008 | Published
Journal Article Open

Towards adiabatic waveforms for inspiral into Kerr black holes. II. Dynamical sources and generic orbits

Abstract

This is the second in a series of papers whose aim is to generate adiabatic gravitational waveforms from the inspiral of stellar-mass compact objects into massive black holes. In earlier work, we presented an accurate (2+1)D finite-difference time-domain code to solve the Teukolsky equation, which evolves curvature perturbations near rotating (Kerr) black holes. The key new ingredient there was a simple but accurate model of the singular source term based on a discrete representation of the Dirac-delta function and its derivatives. Our earlier work was intended as a proof of concept, using simple circular, equatorial geodesic orbits as a test bed. Such a source is effectively static, in that the smaller body remains at the same coordinate radius and orbital inclination over an orbit. (It of course moves through axial angle, but we separate that degree of freedom from the problem. Our numerical grid has only radial, polar, and time coordinates.) We now extend the time-domain code so that it can accommodate dynamic sources that move on a variety of physically interesting world lines. We validate the code with extensive comparison to frequency-domain waveforms for cases in which the source moves along generic (inclined and eccentric) bound geodesic orbits. We also demonstrate the ability of the time-domain code to accommodate sources moving on interesting nongeodesic worldlines. We do this by computing the waveform produced by a test mass following a kludged inspiral trajectory, made of bound geodesic segments driven toward merger by an approximate radiation loss formula.

Additional Information

©2008 The American Physical Society. (Received 3 March 2008; published 11 July 2008) We are very grateful to Jonathan Gair and Kostas Glampedakis for their permission to use the code from Ref. [18] to build the inspiral we use in Sec. IV. P.A.S. and S.A.H. are supported by NASA Grant No. NNG05G105G; S.A.H. is additionally supported by NSF Grant No. PHY-0449884 and the MIT Class of 1956 Career Development fund. G.K. acknowledges research support from the University of Massachusetts and the Fund for Astrophysical Research, Inc., as well as supercomputing support from the TeraGrid (Grant No. TG-PHY060047T), which was used for runs to independently confirm the production results presented here. S.D.'s contribution to this analysis was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration and funded through the internal Human Resources Development Fund Initiative and the LISA Mission Science Office. Some of the supercomputers used in this analysis were provided by funding from the JPL Office of the Chief Information Officer.

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August 22, 2023
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October 16, 2023