Studies of waveform requirements for intermediate mass-ratio coalescence searches with advanced gravitational-wave detectors

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The coalescence of a stellar-mass compact object into an intermediate-mass black hole (intermediate mass-ratio coalescence; IMRAC) is an important astrophysical source for ground-based gravitational-wave interferometers in the so-called advanced (or second-generation) configuration. However, the ability to carry out effective matched-filter-based searches for these systems is limited by the lack of reliable waveforms. Here we consider binaries in which the intermediate-mass black hole has a mass in the range 24 M ⊙-200 M⊙ with a stellar-mass companion having masses in the range 1.4 M ⊙-18.5 M⊙. In addition, we constrain the mass ratios, q, of the binaries to be in the range 1/140≤q≤1/10 and we restrict our study to the case of circular binaries with nonspinning components. We investigate the relative contribution to the signal-to-noise ratio (SNR) of the three different phases of the coalescence - inspiral, merger and ringdown - using waveforms computed within the effective one-body formalism matched to numerical relativity. We show that merger and ringdown contribute to a substantial fraction of the total SNR over a large portion of the mass parameter space, although in a limited portion the SNR is dominated by the inspiral phase. We further identify three regions in the IMRAC mass space in which (i) inspiral-only searches could be performed with losses in detection rates L in the range 10%â‰Lâ‰27%, (ii) searches based on inspiral-only templates lead to a loss in detection rates in the range 27%â‰Lâ‰50%, and (iii) templates that include merger and ringdown are essential to prevent losses in detection rates greater than 50%. In addition we find that using inspiral-only templates as filters can lead to large biases in the estimates of the mass parameters of IMRACs. We investigate the effectiveness with which the inspiral-only portion of the IMRAC waveform space is covered by comparing several existing waveform families in this regime. We find that different waveform families are only marginally effective at describing one another, as measured by the "fitting factor." Our results reinforce the importance of extensive numerical relativity simulations of IMRACs to validate and calibrate semianalytical waveform families and the need for further studies of suitable approximation schemes in this mass range. Published by the American Physical Society.

Original languageEnglish
Article number044010
Number of pages10
JournalPhysical Review D
Issue number4
Publication statusPublished - 5 Aug 2013


  • gravitational waves
  • gravitational self-force
  • black holes (astronomy)

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