Infrared identification of 2XMM J191043.4+091629.4

¹ Department of Physics, Systems Engineering and Signal TheoryUniversity of Alicante, 03080 Alicante, Spain
e-mail: rodes@dfists.ua.es
² University Institute of Physics Applied to Sciences and Technologies, University of Alicante, 03080 Alicante, Spain
³ Telescopio Nazionale Galileo, Rambla José Ana Fernández Pérez, 38712 Breña Baja, Spain

Received: 20 May 2013
Accepted: 15 June 2013

Abstract

Context. 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.

Aims. 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.

Methods. 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.

Results. We have shown that the Brackett γ H i at 2.165 μm, and He i at 2.184 μm and at 2.058 μm 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 ± 0.5 kpc. This would be, therefore, the first high-mass X-ray binary in the Outer Arm at galactic longitudes of between 30° and 60°.