UKIRT IR spectra of the microquasar GRS 1915+105

The UKIRT JHK-band spectrum of GRS 1915+105 shows strong He I (2.059 μm) and Brγ (2.166 μm) emission lines. Eikenberry et al. (1998) found flux variations of a factor of 5 in these lines on a 5 min timescale. Based on the detection or not of the He II emission line, it was suggested that the companion could be a LMXB or a HMXB, respectively. Since the spectral type of the companion star of GRS 1915+105 is still an open question we attempt to clarify the issue by revisiting the object and comparing the JHK spectrum with that of the Be star DM +49 3718 and the prototype X-ray binary Sco X-1.