Population of persistent high mass X-ray binaries in the Milky Way

TL;DR

This study analyzes the population and distribution of persistent high mass X-ray binaries in the Milky Way using INTEGRAL survey data, revealing their characteristics, spatial distribution, and potential accretion mechanisms.

Contribution

It provides the first comprehensive analysis of persistent HMXBs with a focus on their population, spatial distribution, and accretion processes based on INTEGRAL data.

Findings

Majority of persistent HMXBs have supergiant companions.

Luminosity function steepens around ~2x10^{36} erg/s.

HMXB spatial distribution correlates with star formation rate.

Abstract

We present results of the study of persistent high mass X-ray binaries (HMXBs) in the Milky Way, obtained from the deep INTEGRAL Galactic plane survey. This survey provides us a new insight into the population of high mass X-ray binaries because almost half of the whole sample consists of sources discovered with INTEGRAL. It is demonstrated for the first time that the majority of persistent HMXBs have supergiant companions and their luminosity function steepens somewhere around ~2x10^{36} erg/s. We show that the spatial density distribution of HMXBs correlates well with the star formation rate distribution in the Galaxy. The vertical distribution of HMXBs has a scale-height h~85 pc, that is somewhat larger than the distribution of young stars in the Galaxy. We propose a simple toy model, which adequately describes general properties of HMXBs in which neutron stars accrete a matter from the wind of the its companion (wind-fed NS-HMXBs population). Using the elaborated model we argue that a flaring activity of so-called supergiant fast X-ray transients, the recently recognized sub-sample of HMXBs, is likely related with the magnetic arrest of their accretion.