Suitability of hybrid gravitational waveforms for unequal-mass binaries

TL;DR

This study evaluates the accuracy of hybrid post-Newtonian and numerical relativity waveforms for binary black-hole parameter estimation, highlighting the need for longer NR waveforms at higher mass ratios and the benefits of 4th order post-Newtonian knowledge.

Contribution

It provides new analysis of hybrid waveforms for unequal-mass binaries and assesses the impact of higher-order post-Newtonian terms on waveform accuracy.

Findings

Errors increase with mass ratio at 3.5PN order.

Longer NR waveforms are needed for high-mass-ratio systems.

4th order post-Newtonian improves hybrid waveform accuracy.

Abstract

This article studies sufficient accuracy criteria of hybrid post-Newtonian (PN) and numerical relativity (NR) waveforms for parameter estimation of strong binary black-hole sources in second- generation ground-based gravitational-wave detectors. We investigate equal-mass non-spinning binaries with a new 33-orbit NR waveform, as well as unequal-mass binaries with mass ratios 2, 3, 4 and 6. For equal masses, the 33-orbit NR waveform allows us to recover previous results and to extend the analysis toward matching at lower frequencies. For unequal masses, the errors between different PN approximants increase with mass ratio. Thus, at 3.5PN, hybrids for higher-mass-ratio systems would require NR waveforms with many more gravitational-wave (GW) cycles to guarantee no adverse impact on parameter estimation. Furthermore, we investigate the potential improvement in hybrid waveforms that can be expected from 4th order post-Newtonian waveforms, and find that knowledge of this 4th post-Newtonian order would significantly improve the accuracy of hybrid waveforms.