Circumstellar dust emission in five Large Magellanic Cloud supergiants

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Abstract
Spectra at 8–13 μm are presented of five Large Magellanic Cloud supergiant stars with circumstellar dust emission. The brightest two objects were discovered in the IRAS survey and have thick dust shells with deep silicate absorption features; they are probably late-type M supergiants undergoing very heavy mass loss. Comparison between the current data and previous mid-infrared photometry suggests that the apparent depth of the silicate feature in the OH/IR star IRAS 04553–6825 has varied over a 5-yr interval. The peculiar B[e] hypergiant R 126 displays a strong circumstellar dust shell, but with a very muted silicate emission feature. The G supergiant R 150 and the luminous blue variable star 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 silicate features indicate that the material lost from the stars is oxygen-rich, in agreement with stellar evolution models.

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