Gravitational-wave template banks for novel compact binaries

TL;DR

This paper presents a new efficient method for generating gravitational-wave template banks for binary black hole mergers, capable of handling complex systems with precession, higher-order modes, and eccentricity, significantly improving search capabilities.

Contribution

The authors introduce a novel metric approximation and use normalizing flow models to rapidly produce high-dimensional template banks, enabling advanced gravitational-wave searches.

Findings

Successfully generated template banks with high coverage and low mismatch.

Achieved rapid bank creation in hours for millions of templates.

Validated the method's effectiveness for precessing and higher-mode systems.

Abstract

We introduce a novel method to generate a bank of gravitational-waveform templates of binary black hole (BBH) mergers for matched-filter searches in LIGO, Virgo and Kagra data.We derive a novel expression for the metric approximation to the distance between templates, which is suitable for precessing BBHs and/or systems with higher-order modes (HM) imprints and we use it to meaningfully define a template probability density across the parameter space. We employ a masked autoregressive normalizing flow model which can be conveniently trained to quickly reproduce the target probability distribution and sample templates from it. Thanks to the normalizing flow, our code takes a few {\it hours} to produce random template banks with millions of templates, making it particularly suitable for high-dimensional spaces, such as those associated to precession, eccentricity and/or HM. After validating the performance of our method, we generate a bank for precessing black holes and a bank for aligned-spin binaries with HMs: with only 5% of the injections with fitting factor below the target of 0.97, we show that both banks cover satisfactorily the space. Our publicly released code mbank will enable searches of high-dimensional regions of BBH signal space, hitherto unfeasible due to the prohibitive cost of bank generation.