Supergiant Fast X-ray Transients: A new class of high mass X-ray binaries unveiled by INTEGRAL

TL;DR

This paper introduces Supergiant Fast X-ray Transients (SFXTs), a new class of high mass X-ray binaries characterized by rapid, recurrent X-ray outbursts associated with OB supergiants, expanding our understanding of X-ray binary populations.

Contribution

The study identifies and characterizes SFXTs as a distinct class of high mass X-ray binaries linked to OB supergiants, based on INTEGRAL observations.

Findings

SFXTs exhibit short, recurrent X-ray outbursts.

Many transient X-ray sources share SFXT characteristics.

SFXTs may constitute a major class of X-ray binaries.

Abstract

INTEGRAL monitoring of the Galactic Plane is revealing a growing number of recurrent X-ray transients, characterised by short outbursts with very fast rise times (~ tens of minutes) and typical durations of a few hours. Here we show that several of these transients are associated with OB supergiants and hence define a new class of massive X-ray binaries which we call Supergiant Fast X-ray Transients (SFXTs). Many other transient X-ray sources display similar X-ray characteristics, suggesting that they belong to the same class. Since they are difficult to detect and their number is growing fast and steadily, they could represent a major class of X-ray binaries.