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The strong stellar winds and supernovae of the most massive stars dominate the energy transfer from the stellar to gaseous component of normal galaxies, driving star formation and galaxy evolution. This interaction is manifested on many scales, starting with individual stellar wind bubbles seen around O stars and Wolf-Rayet stars, to galactic superwinds around starburst galaxies. The form of this phenomenon most typically observed is the ``superbubble'' \hii\ region often seen around ordinary OB associations. Since the majority of massive stars are found in these associations, these clusters dominate the input of kinetic energy into the interstellar medium (ISM). Hence, understanding the dynamics and evolution of such superbubbles is essential in understanding the structure and dynamics of the ISM.
Many superbubble \hii\ regions are observed in the Large Magellanic Cloud (LMC), which presents an ideal opportunity to study in detail both the stellar content of the parent OB cluster and the physical conditions of the gaseous shell. I am studying the stellar contents in a sample of 8 LMC superbubble systems, with both broadband $UBV$ photometry and spectral classifications of the hottest stars. As part of the analysis of these stars, I present HR diagrams of the associations in these evolved \hii\ regions.
The stellar wind power which is input to the bubble can be well-constrained from the spectral classifications of the dominant stars. It is then possible to model the shell evolution using analytical formulations, and compare these models to the observed nebular properties. The first system to be studied in detail (with P. Massey, NOAO) is Shapley's Constellation I, containing the association LH47 in the nebula N44.
This work was supported by an AAUW American Fellowship, the U. Arizona Graduate College, and NSF grant AST90-19150.
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