Analysis of the three high-velocity B stars HD 125924, 165955 and CPD – 72° 1184

We analyse optical and IUE observations of three B stars which have extremely high radial velocities but which are otherwise apparently normal. The radial velocities are: for HD 125924, +252 km s−1; for HD 165955, −160 km s−1; and for CPD – 72° 1184, −217 km s−1. We find no evidence for any strong deviation from population I abundances in up to 10 elements. Consequently, the three stars cannot be subluminous members of population II, akin to the UV-bright stars observed in some globular clusters, nor, because of their radial velocities, can they be subluminous members of an old disc population with a radial velocity dispersion of ∼ 30 km s−1, as hypothesized by Carrasco et al. to explain the high velocity OB stars. Observations of interstellar line absorptions are available for HD 125924 and 165955 and are suggestive of normal luminosity. A number of specific tests fail to discriminate between normal and subluminosity: in particular, uncertainties in dE(B–V)/dNH do not allow a comparison between the stellar reddening and the reddening to infinity. If the programme stars are normal, their known kinematics essentially permit an origin in the plane and subsequent ejection at high velocity to their present locations within their evolutionary lifetimes, though the observed proper motions of HD 125924 marginally favour an origin outside the galactic plane, or subluminosity. We conclude that it is most probable that HD 125924, 165955 and CPD – 72° 1184 are not subluminous but are normal population I B stars that have somehow attained extreme velocities, and that it is these extreme velocities which need explanation.