On the Mass Distribution and Birth Masses of Neutron Stars

TL;DR

This paper analyzes neutron star mass distributions across different binary populations using Bayesian methods, revealing distinct formation and accretion histories with implications for neutron star evolution.

Contribution

It provides a detailed statistical analysis of neutron star masses in various populations, highlighting differences in their formation channels and accretion histories.

Findings

Non-recycled neutron stars have a mean mass of 1.28 M_solar.

Double neutron stars have a very narrow mass distribution peaking at 1.33 M_solar.

Recycled neutron stars have a higher mean mass of 1.48 M_solar and a broader distribution.

Abstract

We investigate the distribution of neutron star masses in different populations of binaries, employing Bayesian statistical techniques. In particular, we explore the differences in neutron star masses between sources that have experienced distinct evolutionary paths and accretion episodes. We find that the distribution of neutron star masses in non-recycled eclipsing high-mass binaries as well as of slow pulsars, which are all believed to be near their birth masses, has a mean of 1.28 M_solar and a dispersion of 0.24 M_solar. These values are consistent with expectations for neutron star formation in core-collapse supernovae. On the other hand, double neutron stars, which are also believed to be near their birth masses, have a much narrower mass distribution, peaking at 1.33 M_solar but with a dispersion of only 0.05 M_solar. Such a small dispersion cannot easily be understood and perhaps points to a particular and rare formation channel. The mass distribution of neutron stars that have been recycled has a mean of 1.48 M_solar and a dispersion of 0.2 M_solar, consistent with the expectation that they have experienced extended mass accretion episodes. The fact that only a very small fraction of recycled neutron stars in the inferred distribution have masses that exceed ~2 M_solar suggests that only a few of these neutron stars cross the mass threshold to form low mass black holes.