Astrophysical Uncertainties in the Gravitational-Wave Background from Stellar-Mass Compact Binary Mergers

TL;DR

This paper models the stochastic gravitational wave background from stellar-mass compact binary mergers, analyzing astrophysical uncertainties and predicting detection prospects for LIGO/Virgo/Kagra and LISA.

Contribution

It introduces three analytical and three population synthesis models to quantify uncertainties in the astrophysical gravitational-wave background from binary mergers.

Findings

Predicted Omega_GW ranges for BBHs at different frequencies.

Background unlikely detectable in current LIGO/Virgo/Kagra run.

Potential detectability of the background with LISA.

Abstract

We investigate the Stochastic Gravitational Wave Background (SGWB) produced by merging binary black holes (BBHs) and binary neutron stars (BNSs) in the frequency ranges of LIGO/Virgo/Kagra and LISA. We develop three analytical models, that are calibrated to the measured local merger rates, and complement them with three population synthesis models based on the COSMIC code. We discuss the uncertainties, focusing on the impact of the BBH mass distribution, the effect of the metallicity of the progenitor stars and the time delay distribution between star formation and compact binary merger. We also explore the effect of uncertainties in binary stellar evolution on the background. For BBHs, our analytical models predict $\Omega_{GW}$ in the range $[4.10^{-10}-1.10^{-9}]$ (25 Hz) and $[1.10^{-12}-4.10^{-12}]$ (3 mHz), and between $[2.10^{-10}-2.10^{-9}]$ (25 Hz) and $[7.10^{-13}- 7.10^{-12}]$ (3 mHz) for our population synthesis models. This background is unlikely to be detected during the LIGO/Virgo/Kagra O4 run, but could be detectable with LISA. We predict about 10 BBH and no BNS mergers that could be individually detectable by LISA for a period of observation of 4 years. Our study provides new insights into the population of compact binaries and the main sources of uncertainty in the astrophysical SGWB.