Issei Yamamura 1,2 - Teije de Jong 2,3 - Kay Justtanont 2 - Jan Cami 2,3 - Rens Waters 2,3
1 Department of Astronomy, University. of Tokyo, Japan -We report the preliminary result of SWS observation of a silicate carbon star V778 Cyg. Silicate carbon stars were discovered in the studies of IRAS Low Resolution Spectra (Willems and de Jong 1986, Little-Marenin 1986). They show silicate dust emission features at 10 and 18 micron which are the characteristics of oxygen-rich circumstellar envelopes, while the central stars have properties of carbon stars. Detailed spectroscopic studies (e.g., Lloyd Evans 1990) revealed that the central stars are usually 13C rich (i.e. J-type stars). Several explanations about the origin of the silicate feature have been proposed, such as quick transition from oxygen-rich to carbon-rich (Willems and de Jong 1986), binary with a oxygen-rich giant (Little-Marenin 1986), or a disk around a companion (Morris 1987). We observed one of such stars in the guaranteed time program AGBSTARS (P.I. T. de Jong). The observation was carried out by SWS AOT01 speed 3, with a spectral resolution of about 700. Results of comparison with templates of carbon-rich and oxygen-rich stars are presented and the implications for the origin of silicate carbon stars will be discussed.
Postscript version