A radial velocity study of three WN stars and an O3f star in the Carina Nebula

Spectroscopic data and radial-velocity observations are presented for the O3 If star HD 93129 and the WN-A stars HD 92740, HD 93131, and HD 93162, all four of which are members of the very young Carina Nebula association. HD 92740 is found to be a single-lined spectroscopic binary with an eccentric orbit, a period of about 80 days, and emission and absorption lines that vary in phase. The results indicate that the remaining three stars appear to be single and that the narrow emission lines observed in HD 93131 and HD 93162 seem to give the velocities of the stars themselves. Envelope structures and the probable evolutionary status of these stars are discussed. It is concluded that the radial velocities are consistent with the existence of a physical connection, perhaps evolutionary, between the O3 If and WN-A stars, that a binary nature is evidently not a necessary condition for a late-type Population I WN star, and that very massive single stars can apparently develop into WN stars.