Expected number of supergiant fast X-ray transients in the Milky Way

Abstract

In the past fifteen years a new generation of X-ray satellites led to the discovery of a subclass of high-mass X-ray binaries (HMXBs) with supergiant companions and a peculiar transient behaviour: supergiant fast X-ray transients (SFXTs). We calculate the expected number of Galactic SFXTs for the first time, using two different statistical approaches and two sets of data based on Swift and INTEGRAL surveys, with the aim to determine how common the SFXT phenomenon really is. We find that the expected number of SFXTs in the Galaxy is about 37(+53, -22) which shows that SFXTs constitute a large portion of X-ray binaries with supergiant companions in the Galaxy. We compare our estimate with the expected number of Galactic HMXBs predicted from observations and evolutionary models and discuss the implications for the nature of SFXTs.

Accepted for publication in Astronomy and Astrophysics. 5 pages

References in corpus (19)

• Catalogue of high-mass X-ray binaries in the Galaxy ($4^{th}$ edition)
• Probing clumpy stellar winds with a neutron star
• Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. I. The nature of the companion star
• High variability in Vela X-1: giant flares and off states
• Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. II. The environment of the companion star
• An alternative hypothesis for the outburst mechanism in Supergiant Fast X-ray Transients: the case of IGR J11215-5952
• INTEGRAL/IBIS nine-year Galactic Hard X-Ray Survey
• A description of sources detected by INTEGRAL during the first 4 years of observations
• Monitoring Supergiant Fast X-ray Transients with Swift. I. Behavior outside outbursts
• Distribution of High-Mass X-ray Binaries in the Milky Way
• Swift/XRT observes the fifth outburst of the periodic Supergiant Fast X-ray Transient IGR J11215-5952
• IGR J11215-5952: a hard X-ray transient displaying recurrent outbursts
• Monitoring Supergiant Fast X-ray Transients with Swift. Rise to the outburst in IGR J16479-4514
• A Search for New Galactic Magnetars in Archival Chandra and XMM-Newton Observations
• Supergiant Fast X-ray Transients and Other Wind Accretors
• Supergiant, fast, but not so transient 4U 1907+09
• Optical/infrared observations unveiling the formation, nature and evolution of High-Mass X-ray Binaries
• Population of the Galactic X-ray binaries and eRosita
• A Transient Supergiant X-ray Binary in IC10. An Extragalactic SFXT?

Cited by in corpus (8)

• Seven Years with the Swift Supergiant Fast X-ray Transients Project
• Supergiant fast X-ray transients as an under-luminous class of supergiant X-ray binaries
• The Effect of Variability on X-Ray Binary Luminosity Functions: Multiple Epoch Observations of NGC 300 with Chandra
• The 100-month Swift catalogue of supergiant fast X-ray transients II. SFXT diagnostics from outburst properties
• INTEGRAL discovery of unusually long broad-band X-ray activity from the Supergiant Fast X-ray Transient IGR J18483-0311
• X-Ray Views of Galactic Accreting Pulsars in High-Mass X-Ray Binaries
• Searching for supergiant fast X-ray transients with Swift
• Monitoring the X-ray Variability of Bright X-ray Sources in M33