One of the most recent discoveries of the INTEGRAL observatory is the existence of a previously unknown population of X-ray sources in the inner arms of the Galaxy . IGR J17544 $ - $ 2619 , IGR~J16465 $ - $ 4507 and XTE~J1739 $ - $ 302 are among these sources .
Although the nature of these systems is still unexplained , the investigations of the optical/NIR counterparts of the two last sources , combined with high energy data , have provided evidence of them being highly absorbed high mass X-ray binaries with blue supergiant secondaries and displaying fast X-ray transient behaviour .
In this work we present our optical/NIR observations of IGR J17544 $ - $ 2619 , aimed at identifying and characterizing its counterpart .
We show that the source is a high mass X-ray binary at a distance of 2–4 kpc with a strongly absorbed O9Ib secondary , and discuss the nature of the system .