Galactic hard X-ray sources discovered by INTEGRAL brought to light by multi-wavelength observations II. The environment of the companion star
Résumé
(abridged) Context: The INTEGRAL mission has led to the discovery of a new type of Supergiant X-ray Binaries (SGXBs) whose physical properties differ from those of previously known SGXBs. Two classes are appearing. The first class is constituted of obscured persistent SGXBs and the second class is populated by the so-called Supergiant Fast X-ray Transients (SFXTs). Aims: We report here on mid-infrared (MIR) observations of the companion stars of twelve SGXBs from these two classes. Methods: We used data from observations we carried out at ESO/VLT using VISIR as well as archival and published data to perform broad-band Spectral Energy Distributions of the companion stars and fitted them with a combination of two black-bodies representing the star and a MIR excess due to the absorbing material enshrouding the star, if any. Results: We detect a MIR excess in the emission of IGR~J16318-4848, IGR~J16358-4726 and perhaps IGR~J16195-4945. The other sources do not exhibit any MIR excess even when the intrinsic absorption is very high.
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