Best chirplet chain: near-optimal detection of gravitational wave chirps

TL;DR

This paper introduces a near-optimal detection method for gravitational wave chirps using a pattern search in the time-frequency plane, reducing computational complexity while maintaining detection performance.

Contribution

It proposes a novel near-optimal detection algorithm for unknown GW chirps based on a pattern search approach, improving computational feasibility over exhaustive template matching.

Findings

The method achieves detection performance close to the optimal matched filter approach.

It significantly reduces computational complexity in detecting unknown GW chirps.

The approach is adaptable to a wide class of physically realistic gravitational wave signals.

Abstract

The list of putative sources of gravitational waves possibly detected by the ongoing worldwide network of large scale interferometers has been continuously growing in the last years. For some of them, the detection is made difficult by the lack of a complete information about the expected signal. We concentrate on the case where the expected GW is a quasi-periodic frequency modulated signal i.e., a chirp. In this article, we address the question of detecting an a priori unknown GW chirp. We introduce a general chirp model and claim that it includes all physically realistic GW chirps. We produce a finite grid of template waveforms which samples the resulting set of possible chirps. If we follow the classical approach (used for the detection of inspiralling binary chirps, for instance), we would build a bank of quadrature matched filters comparing the data to each of the templates of this grid. The detection would then be achieved by thresholding the output, the maximum giving the individual which best fits the data. In the present case, this exhaustive search is not tractable because of the very large number of templates in the grid. We show that the exhaustive search can be reformulated (using approximations) as a pattern search in the time-frequency plane. This motivates an approximate but feasible alternative solution which is clearly linked to the optimal one. [abridged version of the abstract]