Phase decomposition of the template metric for continuous gravitational-wave searches

TL;DR

This paper introduces a phase decomposition method that makes the template metric analytically computable for continuous gravitational-wave searches, improving signal detection and noise discrimination.

Contribution

The paper presents a novel phase decomposition technique enabling analytical computation of the template metric in continuous gravitational-wave searches.

Findings

Analytical expression for the phase metric derived.

Enhanced ability to distinguish astrophysical signals from noise.

Improved template grid construction for matched filtering.

Abstract

A type of gravitational-wave signals in the LIGO-Virgo sensitivity band are expected to be emitted by spinning asymmetric neutron stars, with rotational frequencies that could plausibly emit continuous gravitational radiation in the most sensitive band of the LIGO-Virgo detectors. The most important feature of such kind of signals is in their phase evolution, which is stable over a long observation run. When using analysis based on matched filtering, the phase evolution of long-coherent signals is needed to define how to build a proper template grid in order to gain the best signal-to-noise ratio possible. This information is encoded in a matrix called \textit{phase metric}, which characterizes the geometry for the likelihood given by the matched filtering. Most of the times, the metric for long-coherent signals cannot be computed anlaytically and even its numerical computation is not possible due to numerical precision. In this paper we show a general phase decomposition technique able to make the template metric analytically computable. We will also show how this variables can be employed to distinguish in a robust way among astrophysical signals and non-stationary noise artifacts that may affect analysis pipelines.