2000MNRAS.317..158O

We present the first detections of the black hole X-ray binary GRS 1915+105 at submillimetre (submm) wavelengths. We clearly detect the source at 350GHz in two epochs, with significant variability over the 24h between epochs. Quasi-simultaneous radio monitoring indicates an approximately flat spectrum from 2 to 350GHz, although there is marginal evidence for a minimum in the spectrum between 15 and 350GHz. The flat spectrum and correlated variability imply that the submm emission arises from the same synchrotron source as the radio emission. This source is likely to be a quasi-steady partially self-absorbed jet, in which case these submm observations probe significantly closer to the base of the jet than do radio observations and may be used in future as a valuable diagnostic of the disc-jet connection in this source.