Radial velocity study of six known WN3/O3 stars

Our study finds no evidence of statistically significant radial velocity variations, and allows us to set stringent upper limits on the mass of any hypothetical companion star: for probable orbital inclinations, any companion with a period less than 100 days must have a mass <2M_{sun}_. For periods less than 10 days, any companion would have to have a mass <1M_{sun}_. We argue that scenarios where any such companion is a compact object are unlikely.

The absorption lines indicate a normal projected rotational velocity, making it unlikely that these stars evolved with the aid of a companion star that has since merged. The modest rotation also suggests that these stars are not the result of homogenous evolution. Thus it is likely that these stars are a normal but short-lived stage in the evolution of massive stars.