Search for gravitational waves from the coalescence of sub-solar mass and eccentric compact binaries

TL;DR

This study searches for gravitational waves from sub-solar mass black hole mergers with eccentric orbits, aiming to identify primordial black holes as dark matter candidates, but finds no significant signals in LIGO data.

Contribution

First search allowing for eccentricity in sub-solar mass black hole mergers, providing new constraints on primordial black holes as dark matter.

Findings

No convincing gravitational wave candidates found.

Two marginal candidates with low statistical significance.

Upper limits set on sub-solar mass merger rates.

Abstract

We present the first search for gravitational waves from sub-solar mass compact-binary mergers which allows for non-negligible orbital eccentricity. Sub-solar mass black holes are a signature of primordial origin black holes, which may be a component of dark matter. To produce binary coalescences, primordial black holes may form close binaries either in the early universe or more recently through dynamical interactions. A signature of dynamical formation would be the observation of non-circularized orbits. We search for black hole mergers where the primary mass is $0.1-7 M_{\odot}$ and the secondary mass is $0.1-1 M_{\odot}$. We allow for eccentricity up to $\sim0.3$ at a dominant-mode gravitational-wave frequency of 10 Hz for binaries with at least one component with mass $>0.5 M_{\odot}$. We find no convincing candidates in the public LIGO data. The two most promising candidates have a false alarm rate of 1 per 3 and 4 years, respectively, which combined is only a $\sim 2.4\sigma$ deviation from the expected Poisson rate. Given the marginal statistical significance, we place upper limits on the rate of sub-solar mass mergers under the assumption of a null observation and compare how these limits may inform the possible dark matter contribution.