Evolution of Binaries in Dense Stellar Systems

TL;DR

This paper explores how binary star systems in dense stellar environments are dynamically formed, destroyed, and evolve, impacting cluster dynamics and X-ray source populations.

Contribution

It provides a comprehensive overview of binary evolution processes in dense stellar systems, emphasizing the roles of dynamical formation and destruction.

Findings

Destruction of soft binaries acts as an energy sink in clusters.

Most globular clusters are still in the core-contracting phase.

Dynamical formation of triples influences X-ray source development.

Abstract

In contrast to the field, the binaries in dense stellar systems are frequently not primordial, and could be either dynamically formed or significantly altered from their primordial states. Destruction and formation of binaries occur in parallel all the time. The destruction, which constantly removes soft binaries from a binary pool, works as an energy sink and could be a reason for cluster entering the binary-burning phase. The true binary fraction is greater than observed, as a result, the observable binary fraction evolves differently from the predictions. Combined measurements of binary fractions in globular clusters suggest that most of the clusters are still core-contracting. The formation, on other hand, affects most the more evolutionary advanced stars, which significantly enhances the population of X-ray sources in globular clusters. The formation of binaries with a compact objects proceeds mainly through physical collisions, binary-binary and single-binary encounters; however, it is the dynamical formation of triples and multiple encounters that principally determine whether the formed binary will become an X-ray source.