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

Abstract

Optical and IUE observations are analyzed for three high radial velocity stars, HD 125924 (+252 km/s), HD 165955 (-160 km/s), and CPD-72 deg 1184 (-217 km/s). On account of their high velocities and no evidence of abnormal carbon and nitrogen abundances, the stars cannot be subluminous members of an old disc population. Magnesium and silicon levels are normal in each star, as are oxygen and phosphorous levels in CPD-72 deg 1184 and probably iron and aluminum in HD 125924. The interstellar line absorptions indicate that HD 125924 and HD 165955 are of normal luminosity. Based on the population II UV-bright hypothesis, it is concluded the three B stars are normal young population I objects and that their high radial velocities require explanation. Two possibilities are proposed: either the stars were generated from tenuous gas or in high-velocity clouds, or there exists a mechanism capable of ejecting at high velocities early-type stars from their birth places.