TRIGGERED STAR-FORMATION AND THE DYNAMICS OF A SUPERBUBBLE IN THE LMC - THE OB ASSOCIATION LH-47/48 IN DEM-152

We examine the stellar population of an OB association, LH 47/48, which is associated with a superbubble H II region, DEM 152 in the N44 nebular complex of the Large Magellanic Cloud. With CCD photometry and spectroscopy of the massive stars, we find no evidence that an unusual stellar population gave rise to the shell morphology of the gas. The slope of the initial mass function, Gamma = -1.3 +/- 0.2, is consistent with that of other OB associations in the LMC, and there is no significant difference in the initial mass function internal or external to the supershell. The inferred stellar ionizing flux is consistent with the observed nebular Ha flux. We do find evidence for triggered star formation: the H-R diagram suggests an age of greater than or similar to 10 Myr for the population interior to the bubble with more recent, less than or similar to 5 Myr, star formation on the exterior. Using the detailed data on the stellar population, we compare a numerical form of the Weaver et al. (1977) evolutionary model for wind-driven bubbles with the observed shell kinematics. We find a substantial discrepancy: the observed shell radius is too small and/or expansion velocity too large to be explained with this version of the model. We discuss possible explanations for the inconsistency.