Searching for Gravitational Waves from Compact Binaries with Precessing Spins

TL;DR

This paper develops a new search method for gravitational waves from precessing binary systems, improving detection sensitivity for systems with high spin misalignment, especially for neutron-star--black-hole mergers.

Contribution

It introduces a new statistic and template banks for generic precessing spins, enhancing gravitational wave detection capabilities beyond aligned-spin models.

Findings

Improved signal recovery for high-mass ratio, precessing systems up to 60%.

Generic-spin banks increase templates by a factor of 10-20.

Small sensitivity loss (~4%) for well-covered aligned-spin systems.

Abstract

Current searches for gravitational waves from compact-object binaries with the LIGO and Virgo observatories employ waveform models with spins aligned (or anti-aligned) with the orbital angular momentum. Here, we derive a new statistic to search for compact objects carrying generic (precessing) spins. Applying this statistic, we construct banks of both aligned- and generic-spin templates for binary black holes and neutron-star--black-hole binaries, and compare the effectualness of these banks towards simulated populations of generic-spin systems. We then use these banks in a pipeline analysis of Gaussian noise to measure the increase in background incurred by using generic- instead of aligned-spin banks. Although the generic-spin banks have a factor of ten to twenty more templates than the aligned-spin banks, we find an overall improvement in signal recovery at fixed false-alarm rate for systems with high-mass ratio and highly precessing spins ---up to 60\% for neutron-star--black-hole mergers. This gain in sensitivity comes at a small loss of sensitivity ($\lesssim$4\%) for systems that are already well-covered by aligned-spin templates. Since the observation of even a single binary merger with misalinged spins could provide unique astrophysical insights into the formation of these sources, we recommend that the method described here be developed further to mount a viable search for generic-spin binary mergers in LIGO/Virgo data.