Investigating eccentricities of the binary black hole signals from the LIGO-Virgo catalog GWTC-1

TL;DR

This paper evaluates the performance of an eccentric waveform model for binary black hole signals, re-estimates their eccentricities, and discusses implications for black hole formation mechanisms based on gravitational wave data.

Contribution

It introduces and validates the SEOBNRE eccentric waveform model and applies it to re-estimate black hole merger eccentricities from LIGO-Virgo data.

Findings

Most black hole mergers could have initial eccentricities at 10 Hz

Black hole signals are circularized at observed frequencies above 20 Hz

Eccentricities at lower frequencies could support dynamical formation scenarios

Abstract

In the first Gravitational-Wave Transient Catalogue of LIGO and Virgo, all events are announced having zero eccentricity. In the present paper, we investigate the performance of SEOBNRE which is a spin-aligned eccentric waveform model in time-domain. By comparing with all the eccentric waveforms in SXS library, we find that the SEOBNRE coincides perfectly with numerical relativity data. Employing the SEOBNRE, we re-estimate the eccentricities of all black hole merger events. We find that most of these events allow a possibility for existence of initial eccentricities at 10 Hz band, but are totally circularized at the observed frequency ($ \gtrsim 20$ Hz). The upcoming update of LIGO and the next generation detector like as Einstein Telescope, will observe the gravitational waves starting at 10 Hz or even lower. If the eccentricity exists at the lower frequency, it may significantly support the dynamical formation mechanism taking place in globular clusters.