Obscured sources and Supergiant Fast X-ray Transients: new classes of high mass X-ray binaries

TL;DR

This paper reports on the discovery and characterization of two new classes of high-mass X-ray binaries, namely obscured sources and supergiant fast X-ray transients, based on multi-wavelength observations of 21 INTEGRAL sources.

Contribution

It introduces two distinct classes of high-energy binary systems and provides multi-wavelength observational evidence supporting their unique properties.

Findings

Obscured sources are enshrouded by dust and cold gas.

Supergiant fast X-ray transients exhibit rapid X-ray variability.

Multi-wavelength data helps classify and understand these new binary systems.

Abstract

A new type of high-energy binary systems has been revealed by the INTEGRAL satellite. These sources are in the course of being unveiled by means of multi-wavelength optical, near- and mid-infrared observations. Among these sources, two distinct classes are appearing: the first one is constituted of intrinsically obscured high-energy sources, of which IGR J16318-4848 seems to be the most extreme example. The second one is populated by the so-called supergiant fast X-ray transients, with IGR J17544-2619 being the archetype. We report here on multi-wavelength optical to mid-infrared observations of a sample of 21 INTEGRAL sources. We show that in the case of the obscured sources our observations suggest the presence of absorbing material (dust and/or cold gas) enshrouding the whole binary system. We finally discuss the nature of these two different types of sources, in the context of high energy binary systems.