Population properties of neutron stars in the coalescing compact binaries

TL;DR

This study uses hierarchical Bayesian inference on gravitational wave data to analyze the population properties of neutron star-involving binaries, revealing insights into mass distributions, merger rates, and spin orientations.

Contribution

It provides the first comprehensive Bayesian analysis of neutron star binary populations, comparing different mass models and spin configurations using gravitational wave observations.

Findings

Mass distribution models are inconclusive but slightly favor Galactic NSs.

The BH mass distribution in NSBHs resembles that in X-ray binaries.

The NSBH to BNS merger rate ratio is approximately 3:7.

Abstract

We perform a hierarchical Bayesian inference to investigate the population properties of the coalescing compact binaries involving at least one neutron star (NS). With the current observation data, we can not rule out either of the Double Gaussian, Single Gaussian and Uniform NS mass distribution models, although the mass distribution of the Galactic NSs is slightly preferred by the gravitational wave (GW) observations. The mass distribution of black holes (BHs) in the neutron star-black hole (NSBH) population is found to be similar to that for the Galactic X-ray binaries. Additionally, the ratio of the merger rate densities between NSBHs and BNSs is estimated to be about 3 : 7. The spin properties of the binaries, though constrained relatively poor, play nontrivial role in reconstructing the mass distribution of NSs and BHs. We find that a perfectly aligned spin distribution can be ruled out, while a purely isotropic distribution of spin orientation is still allowed.