Abstract
We present a radial velocity study and revised spectral classification for 41 stars in the line of sight to the open cluster Collinder 121, whose existence has been often questionned, as well as its relation to a young stellar association containing the WR star HD 50896 (WR6). From our spectroscopic data and photometry available in the literature we are able to identify a real clustering at a distance of 1.1 +/- 0.2 kpc from the Sun (derived through the spectroscopic parallax of its members) and sharing an average heliocentric radial velocity of 33.9 +/- 2.5 km s^{-1}. This group is coincident in distance with that found by Kaltcheva (2000) based on Strömgren and Hβ photometry. From HIPPARCOS proper motions, available for 19 stars among the cluster probable members included in our study, we also confirm a common spatial kinematics for the group. The radial velocity determined for Collinder 121 is in agreement with that obtained for the ring nebula S 308 (associated to WR 6) and its surrounding HI structure, thus a physical vinculation with the cluster is inferred.
