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

TL;DR

This study classifies three accreting binary systems discovered by INTEGRAL using VLT/X-Shooter spectra, infrared data, and Gaia parallaxes, identifying their specific types and properties for better understanding of high mass X-ray binaries.

Contribution

It provides the first detailed spectral classification of three INTEGRAL-discovered binaries, combining multi-wavelength data to determine their nature and orbital characteristics.

Findings

IGR J10101-5654 and IGR J11435-6109 are BeHMXBs with B0.5Ve stars and peculiar carbon emission.

IGR J12489-6243 is a cataclysmic variable with an evolved K star.

Estimated geometrical parameters of the disk and orbit for IGR J11435-6109.

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 B0.5Ve 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 disk and neutron star's orbit in the case of IGR J11435-6109.