Discovery of the near-infrared counterpart of the X-ray transient XTE J1908+094: The counterpart of XTE J1908+094

Abstract

We report on the identification in the near-infrared (NIR) of the counterpart to the newly discovered black hole candidate XTE J1908+094, achieved partly through ‘Target of Opportunity’ (ToO) observations carried out at the ESO/NTT. Accurate astrometry and photometry performed on three sets of observations of the source covering 1.7 months have shown a decrease of its NIR flux, consistent with the X-ray decay. After dereddening for the measured column density, we computed the absolute magnitudes of the source for different distances. We derive that the source is a low-mass system and that the companion star is a main sequence star with a spectral type later than K.