2013A&A...555A.115R

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 analysed UKIDSS images around the best position of the X-ray source and obtained spectra of the best candidate using NICS in the Telescopio Nazionale Galileo (TNG) 3.5-m telescope. We present photometric and spectroscopic TNG analyses of the infrared counterpart of the X-ray source, identifying emission lines in the K-band. The H-band spectra does not present any significant feature. We have shown that the Brackett γ HI at 2.165µm, and HeI at 2.184µm and at 2.058µm are significantly present in the infrared spectrum. The CO bands are also absent from 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±0.5kpc. This would be, therefore, the first high-mass X-ray binary in the Outer Arm at galactic longitudes of between 30° and 60°.