IR spectra of the microquasar GRS 1915+105 during a low state

There is controversy regarding the nature of the suspected donor star to the microquasar GRS 1915+105, and hence whether GRS 1915+105 is a high mass X-ray binary (HMXB) or a low-mass X-ray binary (LMXB). In order to clarify this issue, we obtained an infrared (J, H and It) spectrum of GRS 1915+105 in its low state which shows a steeper continuum than the prototype X-ray binary Sco X-1. We did not detect ang He II emission at 2.189 mum from GRS 1915+105 in our quiescent spectrum, indicating that the line is transient and is only observed during episodes of high X-ray activity. For our instrument configuration, there is no detection of the (CO)-C-12 lines which are characteristic of late-type stars either in GRS 1915+105 or Sco X-1.