The Probability Distribution of Astrophysical Gravitational-Wave Background Fluctuations

TL;DR

This paper introduces a method to compute the full probability distribution of strain fluctuations in astrophysical gravitational-wave backgrounds, providing insights into their non-Gaussian features and aiding spectral reconstruction.

Contribution

It presents a novel approach to determine the complete strain fluctuation distribution, including analytical asymptotics and numerical evaluation, for stochastic gravitational-wave backgrounds.

Findings

The large strain tail is dominated by the nearest source.

The distribution deviates from Gaussian, especially in the tails.

The method applies to both time series and frequency domain data.

Abstract

The coalescence of compact binary stars is expected to produce a stochastic background of gravitational waves (GW) observable with future GW detectors. Such backgrounds are usually characterized by their power spectrum as a function of frequency. Here, we present a method to calculate the full 1-point distribution of strain fluctuations. We focus on time series data, but our approach generalizes to the frequency domain. We illustrate how this probability distribution can be evaluated numerically. In addition, we derive accurate analytical asymptotic expressions for the large strain tail, which demonstrate that it is dominated by the nearest source. As an application, we calculate the distribution of strain fluctuations for the astrophysical GW background produced by binary mergers of compact stars in the Universe, and the distribution of the observed confusion background obtained upon subtracting bright, resolved sources from the signal. We quantify the extent to which they deviate from a Gaussian distribution. Our approach could be useful for the spectral shape reconstruction of stochastic GW backgrounds.