Spectroscopic identification of INTEGRAL high-energy sources with VLT/ISAAC^⋆

¹ Laboratoire AIM (UMR 7158 CEA/DRF – CNRS – Université Paris Diderot), Irfu/Département d’Astrophysique, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: francis.fortin@cea.fr
² Institut Universitaire de France, 103 Bd Saint-Michel, 75005, Paris, France
³ APC, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, 10 Rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
⁴ Space Science Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450, USA
⁵ Unidad de Astronomía, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1270300, Chile

Received: 29 May 2017
Accepted: 24 July 2018

Abstract

Context. The INTEGRAL satellite has been observing the γ-ray sky for 15 years and has detected over 900 X-ray sources of various nature. However, more than 200 of these sources still lack precise identification.

Aims. Our goal is to reveal the nature of the high-energy sources detected by INTEGRAL. In particular, we want to improve the census of X-ray binaries.

Methods. Photometry and spectroscopy were performed in July 2012 on 14 INTEGRAL sources in near-infrared at the Very Large Telescope on the European Southern Observatory-UT3 telescope equipped with the ISAAC spectrograph. We used K_s images reaching to a depth of magnitude 18.5 to look for unique counterparts to high-energy detections to check for both extended sources and photometric variability. The analysis of near-infrared spectral features allows us to constrain the nature of these X-ray sources by comparing them to stellar spectra atlases.

Results. We present photometric and/or spectroscopic data for 14 sources (IGR J00465–4005, IGR J10447–6027, IGR J12489–6243, IGR J13020–6359, IGR J13186–6257, IGR J15293–5609, IGR J17200–3116, IGR J17404–3655, IGR J17586–2129, IGR J17597–2201, IGR J18457+0244, IGR J18532+0416, IGR J19308+0530, and IGR J19378–0617). We conclude that 5 of these are active galactic nuclei, 5 are cataclysmic variables, 2 are low- or intermediate-mass X-ray binaries, and 2 are Be high-mass X-ray binaries.