Classification of 3 accreting binaries with VLT/X-Shooter spectra

Abstract

ABSTRACT Since its launch, the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite has discovered hundreds of X-ray sources, many of which lack proper classification. This mission also led to the discovery of new categories of high mass X-ray binaries (HMXB). We use the spectra of the X-Shooter instrument at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) to better understand the nature of 3 accreting binaries (IGR J10101−5654, IGR J11435−6109, and IGR J12489−6243) discovered by INTEGRAL. We mainly focused on the lines and continuum from the X-Shooter spectra. We used atlases to constrain the nature of the sources and also complemented the spectra with measurements taken by Spitzer and the Wide-field Infrared Survey Explorer (WISE) in infrared, and parallaxes from Gaia for the distances. We determined the nature of each binary system: a BeHMXB system with a companion star of spectral type B0.5 Ve with peculiar carbon emission for IGR J10101−5654 and IGR J11435−6109, and a CV system with an evolved K star (K0IV–K2IV) for IGR J12489−6243. We also estimated some geometrical parameters of the decretion disc and neutron star’s orbit in the case of IGR J11435−6109.