Upper Limits on the Stochastic Gravitational-Wave Background from Advanced LIGO's First Observing Run

TL;DR

This paper reports a search for the stochastic gravitational-wave background using Advanced LIGO's first observing run data, setting new upper limits on its energy density and implications for black hole populations.

Contribution

It provides the first constraints on the stochastic gravitational-wave background from LIGO's initial data, improving sensitivity by a factor of 33 over previous measurements.

Findings

No evidence of a stochastic gravitational-wave background was found.

The energy density of gravitational waves is constrained to be less than 1.7×10^{-7} at 95% confidence.

Results have implications for the rate and mass distribution of binary black hole mergers.

Abstract

A wide variety of astrophysical and cosmological sources are expected to contribute to a stochastic gravitational-wave background. Following the observations of GW150914 and GW151226, the rate and mass of coalescing binary black holes appear to be greater than many previous expectations. As a result, the stochastic background from unresolved compact binary coalescences is expected to be particularly loud. We perform a search for the isotropic stochastic gravitational-wave background using data from Advanced LIGO's first observing run. The data display no evidence of a stochastic gravitational-wave signal. We constrain the dimensionless energy density of gravitational waves to be $\Omega_0<1.7\times 10^{-7}$ with 95% confidence, assuming a flat energy density spectrum in the most sensitive part of the LIGO band (20-86 Hz). This is a factor of ~33 times more sensitive than previous measurements. We also constrain arbitrary power-law spectra. Finally, we investigate the implications of this search for the background of binary black holes using an astrophysical model for the background.