SHELL FORMATION AND STAR-FORMATION IN SUPERBUBBLE DEM-192

Was star formation in the OB associations, LH 51 and LH 54, triggered by the growth of the superbubble DEM 192? To examine this possibility, we investigate the stellar contents and star formation history and mo del the evolution of the shell. K-R diagrams constructed from UBV phot ometry and spectral classifications indicate highly coeval star format ion, with the entire massive star population having an age of less tha n or similar to 2-3 Myr. However, LH 54 is constrained to an age of si milar to 3 Myr by the presence of a W-R star, and the initial mass fun ction (IMF) for LH 51 suggests a lower mass limit implying an age of 1 -2 Myr. There is no evidence of an earlier stellar population to creat e the superbubble, but the modeled shell kinematics are consistent wit h an origin due to the strongest stellar winds of LH 54. It might ther efore be possible that LH 54 created the superbubble, which in turn ma y have triggered the creation of LH 51. Within the errors, the spatial distribution of stellar masses and IMF appear uniform within the asso ciations. We reinvestigate the estimates for stellar wind power L-w(t) during the H-burning phase and note that revised mass-loss rates yiel d a significantly different form for L-w(t) and may affect stellar evo lution timescales. We also model superbubble expansion into an ambient medium with a sudden, discontinuous drop in density and find that thi s can easily reproduce the anomalously high-shell expansion velocities seen in many superbubbles.