Near-infrared identification of the counterpart to X1908+075: a new OB-supergiant X-ray binary

We report the near-infrared (near-IR) identification of the likely counterpart to X1908+075, a highly absorbed Galactic X-ray source recently suspected to belong to the rare class of OB supergiant-neutron star binary systems. Our JHK(s)-band imaging of the field reveals the existence within the X-ray error boxes of a near-IR source consistent with an early-type star lying at d similar to 7 kpc and suffering A(V) similar to 16 mag of extinction, the latter value being in good agreement with the hydrogen column density derived from modelling of the X-ray spectrum. Our follow-up, near-IR spectroscopic observations confirm the nature of this candidate and lead to a late O-type supergiant classification, thereby supporting the identification of a new Galactic OB-supergiant X-ray binary.