# High-Mass X-ray Binaries: progenitors of double compact objects

## TL;DR

This paper reviews the current understanding of High-Mass X-ray Binaries (HMXBs), their formation pathways, and their evolution into double compact objects like neutron star or black hole binaries, highlighting different evolutionary scenarios.

## Contribution

It provides a comprehensive overview of the formation and evolution of HMXBs into double compact objects, including new insights into stable and unstable evolutionary channels.

## Key findings

- Only long-period HMXBs with neutron stars survive common-envelope evolution.
- Short-period HMXBs evolve into Wolf-Rayet X-ray binaries with black holes.
- Multiple pathways lead to the formation of double black hole or black hole-neutron star binaries.

## Abstract

A summary is given of the present state of our knowledge of High-Mass X-ray Binaries (HMXBs), their formation and expected future evolution. Among the HMXB-systems that contain neutron stars, only those that have orbital periods upwards of one year will survive the Common-Envelope (CE) evolution that follows the HMXB phase. These systems may produce close double neutron stars with eccentric orbits. The HMXBs that contain black holes do not necessarily evolve into a CE phase. Systems with relatively short orbital periods will evolve by stable Roche-lobe overflow to short-period Wolf-Rayet (WR) X-ray binaries containing a black hole. Two other ways for the formation of WR X-ray binaries with black holes are identified: CE-evolution of wide HMXBs and homogeneous evolution of very close systems. In all three cases, the final product of the WR X-ray binary will be a double black hole or a black hole neutron star binary.