MOLECULES IN CIRCUMSTELLAR ENVELOPES OF CARBON STARS

We have searched for line emission from various transitions of a numbe r of molecules, including CO, HCN, CN, CS and SiO, as well as some of their isotopic variants, towards a sample of 68 bright carbon stars. P art of the data has already been published in Olofsson et al. (1993a,b ). The aim of the project is to obtain a better understanding of the c arbon star phenomenon and the processes involved. In particular, we wo uld like to obtain reliable mass loss rates and molecular abundances f or these objects. This requires careful and detailed modelling, which is currently underway. Our hope is that the study of these bright carb on stars will serve as a guide to the study of higher mass loss rate o bjects. Some preliminary observational results are presented here.