Carbon stars with silicate dust in their circumstellar shells

Abstract

Almost all carbon stars having low-resolution spectra obtained with IRAS are surrounded by circumstellar dust shells usually characterized by a very uniform 11.15 μm SiC grain emission feature. About 4% of the C stars show a feature that is shifted to ≡ 11.6 μm. Extraordinarily, three C stars (BM Gem, V778 Cyg, and C1003) are apparently surrounded by oxygen-rich dust shells characterized by strong silicate emission.