Search for Eccentric Black Hole Coalescences during the Third Observing Run of LIGO and Virgo

TL;DR

This study conducted a waveform-independent search for eccentric black hole mergers during LIGO and Virgo's third observing run, finding no new eccentric candidates but setting upper limits on their merger rate.

Contribution

It presents the first observational constraints on high-mass eccentric black hole coalescences using a waveform-independent search during O3.

Findings

No new high-significance eccentric candidates found.

Sensitivity to eccentricities up to 0.3 at 15 Hz was established.

Upper limit on merger rate density for eccentric binaries is 0.33 Gpc$^{-3}$ yr$^{-1}$.

Abstract

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass $M>70$ $M_\odot$) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities $0 < e \leq 0.3$ at $0.33$ Gpc$^{-3}$ yr$^{-1}$ at 90\% confidence level.