The Optical Content of the Error Box of GRS 1915+105

Abstract

We report on deep photometry and spectroscopy of the objects detected in the ROSAT HRI X-ray error box of the hard X-ray transient, GRS 1915+105. The probable counterpart of this source has been detected, with a magnitude of 23.4 in the I band. The optical absorption ${\rm A}_{\rm V} = 28$ derived from the X-ray data implies an absolute magnitude in the I band, ${\rm M}_{\rm I} \approx -6.7$. We present the data for all the objects present in the error box, together with the spectra of the three brightest. Possible spectral types, as well as estimates of the hydrogen column density are derived.