On the Near-infrared Identification of the INTEGRAL Source IGR J16328–4726

The aim of this work is to identify the infrared (IR) counterpart of the Galactic high-mass X-ray binary IGR J16328-4726 discovered by the INTEGRAL satellite, and to derive the extinction and distance to the system. We present new deep sub-arcsecond JHK(s) imaging and low-resolution near-IR spectroscopy in the 1.5 and 2.4. mu m range of IGR J16328-4726. We report the presence of two near-IR stellar sources separated by about 1 ".8 at the location of the unresolved 2MASS source J16323791-4723409, previously considered to be the near-IR counterpart of the X-ray source. From the analysis of their near-IR colors and spectra as well as accurate positions, we uniquely identify the true IR counterpart of IGR J16328-4726. Our 1.5-2.4 mu m spectrum of this star is consistent with the published classification O8Iafpe. Assuming this, and in combination with new JHK(s) photometry, a reddening A(V) = 23.6 +/- 0.7 and a distance of 7.2 +/- 0.3 kpc from the Sun are derived.