GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences

TL;DR

This paper discusses how the detection of neutron star mergers by LIGO and Virgo impacts the expected stochastic gravitational-wave background, suggesting it could be detectable within a few years at advanced sensitivities.

Contribution

It provides the first estimate of the combined astrophysical gravitational-wave background from neutron star and black hole mergers based on recent observations.

Findings

The total background amplitude near 25 Hz is estimated at 1.8×10^{-9}.

The background from neutron star mergers significantly increases the expected total background.

Detection of the combined background could be achieved after 40 months of observation at design sensitivity.

Abstract

The LIGO Scientific and Virgo Collaborations have announced the first detection of gravitational waves from the coalescence of two neutron stars. The merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. The binary neutron star background will add to the background from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations. In the Advanced LIGO-Virgo frequency band most sensitive to stochastic backgrounds (near 25 Hz), we predict a total astrophysical background with amplitude $\Omega_{\rm GW} (f=25 \text{Hz}) = 1.8_{-1.3}^{+2.7} \times 10^{-9}$ with $90\%$ confidence, compared with $\Omega_{\rm GW} (f=25 \text{Hz}) = 1.1_{-0.7}^{+1.2} \times 10^{-9}$ from binary black holes alone. Assuming the most probable rate for compact binary mergers, we find that the total background may be detectable with a signal-to-noise-ratio of 3 after 40 months of total observation time, based on the expected timeline for Advanced LIGO and Virgo to reach their design sensitivity.