We report the discovery of the optical counterpart of the 12.3 s transient X–ray pulsar GS 0834–43 .
We re–analysed archival \R PSPC observations of GS 0834–43 obtaining two new refined positions , \sim 14″ and \sim 18″ away from the previously published one , and a new spin period measurement .
Based on these results we carried out optical and infra–red ( IR ) follow–up observations .
Within the new error circles we found a relatively faint ( V=20.1 ) early type reddened star ( V–R=2.24 ) .
The optical spectrum shows a strong H \alpha emission line .
The IR observations of the field confirm the presence of an IR excess for the H \alpha –emitting star ( K′=11.4 , J–K′=1.94 ) which is likely surrounded by a conspicuous circumstellar envelope .
Spectroscopic and photometric data indicate a B0–2 V–IIIe spectral–type star located at a distance of 3–5 kpc and confirm the Be–star/X–ray binary nature of GS 0834–43 .