N-Band Observation of the Silicate Carbon Star IRAS08002-3803 (Hen 38) with VLTI/MIDI

Abstract

Silicate carbon stars are a puzzle to date, because they exhibit prominent silicate emission features at ∼10 and ∼18 μm despite their carbon-rich photospheres. Since their discovery in the IRAS LRS by Little-Marenin [1] and Willems & de Jong [5], several scenarios have been proposed for these peculiar objects, and the scenarios widely accepted at the moment suggest that silicate carbon stars have a companion, possibly a main-sequence star, and that oxygen-rich material is shed by mass loss when the primary star was an M giant and this oxygen-rich material is stored in a circumbinary disk (Morris [3]; Lloyd-Evans [2]) or in a circumstellar disk around the companion (Yamamura et al. [6]) until the primary star becomes a carbon star. Observations with high spatial resolution within the silicate emission feature in the mid-infrared would be the most direct approach for investigating the dust environment around silicate carbon stars. VLTI/MIDI provides us with an excellent opportunity to directly study the circumstellar environment of silicate carbon stars in the 10 μm region, exactly where silicate emission from the oxygen-rich reservoir is located. Here we present the results of MIDI observations of the silicate carbon star Hen 38 (IRAS08002-3803).