A THIN MOLECULAR SHELL AROUND THE CARBON STAR TT CYG

Interferometric CO(J=1 --> 0 and 2 --> 1) observations reveal a remark ably thin shell of molecular gas around the carbon star TT Cyg, width/ radius less than or similar to 1.'' 3/34 '' approximate to 0.04. It ex pands at approximate to 13 km s(-1), and contains similar to 0.02 M. o f gas provided the CO abundance with respect to H-2 is 10(-3) and the distance is 1 kpc. Only about a quarter of the shell has been mapped, but we infer an overall spherical shell with only small, but clear, de viations at the per cent level. The radial structure of the shell is b arely resolved at the are second level, but there exists weak emission extending a few are seconds inwards from the peak. A drastic change i n mass loss properties, possibly combined with the effects of interact ing winds, provides the most likely explanation to the origin of the s hell.