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The physics and chemistry of circumstellar envelopes of S-stars on the AGB

Published online by Cambridge University Press:  01 February 2008

Sofia Ramstedt ,
Fredrik L. Schöier  and
Hans Olofsson
Sofia Ramstedt
Affiliation:
Dept. of Astronomy, Stockholm University, Roslagstullsbacken 21, SE-10691, Stockholm, Sweden email: sofia@astro.su.se
Fredrik L. Schöier
Affiliation:
Onsala Space Observatory
Hans Olofsson
Affiliation:
Dept. of Astronomy, Stockholm University, Roslagstullsbacken 21, SE-10691, Stockholm, Sweden email: sofia@astro.su.se Onsala Space Observatory
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Abstract

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Presented here are the preliminary results of a long-term study of S-stars on the AGB. S-stars are important as possible transition objects between oxygen-rich M-stars and carbon stars. The aim of the study is to compare results from our newly gathered observational database for the S-stars with those already obtained for the M- and carbon stars. We can thus follow the changes as the stars evolve along the AGB and more firmly establish the suggested M-MS-S-SC-C evolutionary sequence. It will also allow us to determine the relative importance of processes such as non-equilibrium chemistry, grain formation, and photodissociation in regulating the chemistry in circumstellar envelopes of AGB stars.

Keywords

Stars: AGB and post-AGB(stars:) circumstellar matterstars: mass lossstars: abundances
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S251: Organic Matter in Space , February 2008 , pp. 167 - 168
Copyright
Copyright © International Astronomical Union 2008

References

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Schöier, F. L. & Olofsson, H. 2001, A&A, 368, 969Google Scholar
Schöier, F. L, Olofsson, H., & Lundgren, A. A. 2006, A&A, 454, 247Google Scholar