CIRCUMSTELLAR DUST EMISSION IN 5 LARGE MAGELLANIC CLOUD SUPERGIANTS

Spectra at 8-13 mum are presented of five Large Magellanic Cloud super giant stars with circumstellar dust emission. The brightest two object s were discovered in the IRAS survey and have thick dust shells with d eep silicate absorption features; they are probably late-type M superg iants undergoing very heavy mass loss. Comparison between the current data and previous mid-infrared photometry suggests that the apparent d epth of the silicate feature in the OH/IR star IRAS 04553-6825 has var ied over a 5-yr interval. The peculiar B[e] hypergiant R 126 displays a strong circumstellar dust shell, but with a very muted silicate emis sion feature. The G supergiant R 150 and the luminous blue variable st ar R 71 display prominent silicate emission bands, but in both objects there is evidence that the dust distribution increases away from the star, suggesting that the bulk of the dust was produced at a previous evolutionary stage wherein the mass-loss rates were much higher. The s ilicate features indicate that the material lost from the stars is oxy gen-rich, in agreement with stellar evolution models.