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The evolution of a stellar wind bubble in a cloudy medium of 1-10/cu cm mean density is investigated, allowing for the effects of the star's ionizing radiation. The dynamics of the bubble are governed by the effects of photoionization: weak winds produce bubbles which are confined by the pressure of the H II region, whereas strong winds produce bubbles whose size is determined by the photoevaporation and displacement of the clouds. Nebulae around massive stars begin with wind-blown shells, evolve into amorphous H II regions, then ring-like H II regions, then nebulae with stellar ejecta, and finally are swept up by a blast wave when the star explodes as a supernova. Part or all of the ring-like phase may be too faint to observe. Expanding H II shells with masses of the order of 10,000 solar masses are predicted around massive stars, and may account for the shells seen around the supernova remnants HB 21 and W44.
McKee et al. (Thu,) studied this question.