Binary Evolution Constraints from Luminosity Functions of LMXBs

TL;DR

This study investigates the luminosity functions of low-mass X-ray binaries in nearby galaxies and the Milky Way, revealing differences between globular cluster and non-cluster populations that inform binary evolution models.

Contribution

It provides new observational constraints on the shape of the faint end of the LMXB luminosity function, highlighting differences between globular cluster and field populations.

Findings

Faint end of LMXB luminosity function differs between GCs and non-GCs

Globular clusters have fewer faint LMXBs compared to the field

Population differences suggest varied binary evolution pathways

Abstract

The formation and evolution of low-mass X-ray binaries (LMXBs) is not well understood. The properties of a population of LMXBs depend on a number of uncertain aspects of binary evolution, and population studies offers a relatively new way of probing binary interactions. We have studied the shape of the faint end of the X-ray luminosity function (LF) of LMXBs in nearby galaxies with Chandra and in the Milky Way using the Swift all-sky monitor. We find a clear difference between the LF of LMXBs in globular clusters (GCs) and those outside, with a relative lack of faint GC sources. This indicates a difference in the composition of the two populations.