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Astron. Astrophys. 330, 676-684 (1998)

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Silicon and sulphur chemistry in the inner wind of IRC+10216 *

Karen Willacy and Isabelle Cherchneff

Department of Physics, UMIST, P.O. Box 88, Manchester M60 1QD, UK

Received 5 June 1997 / Accepted 22 August 1997


We present a dynamical and chemical model of the inner wind of the carbon-rich, AGB star IRC+10216. We include the effect of pulsation-driven shocks on the gas envelope close to the stellar photosphere and construct an extended chemical model that includes in particular the chemistry of hydrocarbon species and silicon and sulphur-bearing molecules. The derived theoretical abundances for many molecules are in excellent agreement with values obtained from observations of infrared ro-vibrational molecular lines. We confirm the "parent" character of certain chemical species and show that the inner wind of IRC+10216, and more generally of evolved AGB stars, is an active dynamical and chemical region where molecules are formed and processed.

Key words: molecular processes – stars: AGB – stars: individual: IRC+10216

* Table 5 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr ( or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: I. Cherchneff

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© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998