  Here we report the infrared identification of the X-ray source 2XMM
J191043.4+091629.4, which was detected by XMM-Newton/EPIC in the vicinity of
the Galactic supernova remnant W49B. The aim of this work is to establish the
nature of the X-ray source 2XMM J191043.4+091629.4 studying both the infrared
photometry and spectroscopy of the companion. We analyse UKIDSS images around
the best position of the X-ray source, and obtain spectra of the best candidate
using NICS in the 3.5 m TNG telescope. We present both photometric and
spectroscopic TNG analysis of the infrared counterpart of the X-ray source
identifying emission lines in the K-band. H-band spectra does not present any
significant feature. We have showed that Brackett gamma H I, at 2.165
micrometre, and He I, at 2.184 micrometre and at 2.058 micrometre, are present
significantly in the infrared spectrum. The CO bands are also not present in
our spectrum. Based on these results and the X-ray characteristics of the
source we conclude that the infrared counterpart is an early B-type supergiant
star with an E(B-V)= 7.6 +/- 0.3 at a distance of 16.0 +/- 0.5 kpc. This would
be, therefore, the first high-mass X-ray binary in the Outer Arm at galactic
longitudes between 30 and 60 degrees.
