O-STAR GIANT BUBBLES IN M33

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