Binary evolution and neutron stars in globular clusters

TL;DR

This paper reviews how stellar interactions in globular clusters lead to the formation of neutron star binaries and related sources, supported by recent observations and theoretical considerations.

Contribution

It provides a comprehensive analysis of binary evolution pathways and the impact of cluster dynamics on neutron star populations in globular clusters.

Findings

Radio pulsars and X-ray sources are prevalent in globular clusters.

Close encounters significantly influence binary formation rates.

Black holes are rare in Milky Way globular clusters, consistent with expectations.

Abstract

Improved observations of globular clusters are uncovering a large number of radio pulsars and of X-ray sources. The latter include binaries in which a neutron star or a white dwarf accretes matter from a companion, recycled pulsars, and magnetically active binaries. Most of these sources originate from close encounters between stars in the cluster core; magnetically active binaries and some cataclysmic variables have evolved from primordial binaries. The formation rate through close encounters scales differently with the central density and core radius of the cluster than the probability for a single binary to be perturbed by an encounter. This is exploited in some preliminary observational tests of the close encounter hypothesis. Accreting black holes have been found in globular clusters with other galaxies; the absence of such holes in the Milky Way clusters is compatible with the small number expected.