Searching for the full symphony of black hole binary mergers

TL;DR

This paper introduces a new gravitational-wave search method that incorporates higher-order modes, significantly improving detection sensitivity for certain high-mass, high-mass-ratio black hole mergers.

Contribution

The authors develop and evaluate a novel search technique including higher-order modes, enhancing sensitivity especially for high-mass, high-ratio binary mergers.

Findings

Sensitivity increases up to a factor of 2 in volume for high-mass, high-ratio systems.

Modest sensitivity gains (<10%) for equal-mass or ~50 solar mass systems.

Existing searches perform well for systems with equal masses or lower total mass.

Abstract

Current searches for the gravitational-wave signature of compact binary mergers rely on matched-filtering data from interferometric observatories with sets of modelled gravitational waveforms. These searches currently use model waveforms that do not include the higher-order mode content of the gravitational-wave signal. Higher-order modes are important for many compact binary mergers and their omission reduces the sensitivity to such sources. In this work we explore the sensitivity loss incurred from omitting higher-order modes. We present a new method for searching for compact binary mergers using waveforms that include higher-order mode effects, and evaluate the sensitivity increase that using our new method would allow. We find that, when evaluating sensitivity at a constant rate-of-false alarm, and when including the fact that signal-consistency tests can reject some signals that include higher-order mode content, we observe a sensitivity increase of up to a factor of 2 in volume for high mass ratio, high total-mass systems. For systems with equal mass, or with total mass $\sim 50 M_{\odot}$, we see more modest sensitivity increases, $< 10\%$, which indicates that the existing search is already performing well. Our new search method is also directly applicable in searches for generic compact binaries.