First eccentric inspiral-merger-ringdown analysis of neutron star-black hole mergers

TL;DR

This paper presents the first comprehensive analysis of neutron star-black hole mergers using an aligned-spin eccentric waveform model, confirming eccentricity in GW200105 and finding no eccentricity in other events.

Contribution

It introduces a full inspiral-merger-ringdown eccentric waveform model calibrated to simulations, advancing the analysis of NSBH mergers.

Findings

GW200105 shows strong evidence of eccentricity.

GW200115 and GW230529 are consistent with zero eccentricity.

The analysis highlights computational challenges with eccentric waveform models.

Abstract

The gravitational wave event GW200105 was the first confident neutron star-black hole (NSBH) merger identified by the LIGO-Virgo-KAGRA collaboration. A recent analysis by Morras et al. with an eccentric precessing waveform model that describes the inspiral phase of the $l=2$ and $m=\{0,\pm 2\}$ modes has identified this event as the first NSBH merger with strong evidence of orbital eccentricity. In this paper we perform the first analysis of this event with an aligned-spin eccentric waveform model that describes the full inspiral, merger, and ringdown, includes subdominant harmonics, and is partially calibrated to numerical relativity simulations. This analysis confirms the results and finds evidence in favor of eccentricity even with a log-uniform prior in eccentricity. We also analyze the NSBH events GW200115 and GW230529, completing the analysis of all NSBHs with IMRPhenomTEHM, and find that these signal are consistent with vanishing eccentricity. Finally, we briefly discuss computational challenges when performing the analysis with time-domain eccentric waveform models.