The Impact of Astrophysical Priors on Parameter Inference for GW230529

TL;DR

This study examines how different astrophysical priors influence the inferred masses and spins of components in the GW230529 neutron star-black hole merger, highlighting the significant impact of spin priors on parameter estimation.

Contribution

The paper introduces a detailed analysis of how astrophysical priors, especially on spins, affect gravitational wave parameter inference for GW230529, using models based on binary evolution and pulsar observations.

Findings

Inferred mass distributions depend strongly on spin priors.

Restrictive binary evolution models produce narrower mass distributions.

Black hole spin has a greater impact on mass inference than neutron star spin.

Abstract

We investigate the effects of prior selection on the inferred mass and spin parameters of the neutron star-black hole merger GW230529\_181500. Specifically, we explore models motivated by astrophysical considerations, including massive binary and pulsar evolution. We examine mass and spin distributions of neutron stars constrained by radio pulsar observations, alongside black hole spin observations from previous gravitational wave detections. We show that the inferred mass distribution highly depends upon the spin prior. Specifically, under the most restrictive, binary stellar evolution models, we obtain narrower distributions of masses with a black hole mass of $4.3^{+0.1}_{-0.1}\,M_{\odot}$and neutron star mass of $1.3^{+0.03}_{-0.03}\,M_{\odot}$ where, somewhat surprisingly, it is the prior on component spins which has the greatest impact on the inferred mass distributions. Re-weighting using neutron star mass and spin priors from observations of radio pulsars, with black hole spins from observations of gravitational waves, yields the black hole and the neutron star masses to be $3.8^{+0.5}_{-0.6} \,M_\odot$ and $1.4^{+0.2}_{-0.1} \,M_\odot$ respectively. The sequence of compact object formation -- whether the neutron star or the black hole formed first -- cannot be determined at the observed signal-to-noise ratio. However, there is no evidence that the black hole was tidally spun up.