High Mass X-ray Binaries: Progenitors of double neutron star systems

TL;DR

This review discusses the different types of High-Mass X-ray Binaries (HMXBs), recent discoveries of supergiant HMXBs, their characteristics, and their significance as progenitors of double neutron star systems and related phenomena.

Contribution

It provides a comprehensive overview of HMXB types, introduces new populations of supergiant HMXBs, and discusses their role in the formation of double neutron star systems.

Findings

Discovery of new supergiant HMXB populations

Characterization of supergiant HMXB types and behaviors

Implications for neutron star progenitor evolution

Abstract

In this review I briefly describe the nature of the three kinds of High-Mass X-ray Binaries (HMXBs), accreting through: (i) Be circumstellar disc, (ii) supergiant stellar wind, and (iii) Roche lobe filling supergiants. A previously unknown population of HMXBs hosting supergiant stars has been revealed in the last years, with multi-wavelength campaigns including high energy (INTEGRAL, Swift, XMM, Chandra) and optical/infrared (mainly ESO) observations. This population is divided between obscured supergiant HMXBs, and supergiant fast X-ray transients (SFXTs), characterized by short and intense X-ray flares. I discuss the characteristics of these types of supergiant HMXBs, propose a scenario describing the properties of these high-energy sources, and finally show how the observations can constrain the accretion models (e.g. clumpy winds, magneto-centrifugal barrier, transitory accretion disc, etc). Because they are the likely progenitors of Luminous Blue Variables (LBVs), and also of double neutron star systems, related to short/hard gamma-ray bursts, the knowledge of the formation and evolution of this HMXB population is of prime importance.