O Star Giant Bubbles in M33

M.S. Oey & P. Massey

We have studied two remarkable, giant (130 pc diameter) H-alpha bubble nebulae in M33, and have spectroscopically identified a single, dominant O9 star centrally located in each. We compare the nebular parameters with those predicted by analytical models of wind-blown bubbles, taking into account the evolution of wind power from the parent stars. The agreement is good, suggesting that these objects provide a compelling record of the effect that individual, normal OB stars have on the interstellar medium. The study of such nebulae can provide insight on the evolution of the parent star and its winds.