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Astron. Astrophys. 358, L25-L28 (2000)
Letter to the Editor
HCN in the inner envelope of ![[FORMULA]](img1.gif)
Cygni
D. Duari 1,2 and
J. Hatchell 1
1 Department of Physics, UMIST, P O Box 88, Manchester M60 1QD, UK
2 The Birla Institute of Astronomy and Planetary Sciences, Calcutta 700 071, India
Received 6 March 2000 / Accepted 9 May 2000
Abstract
We have detected the ![[FORMULA]](img2.gif)
and
![[FORMULA]](img3.gif)
transitions of HCN towards the S star
![[FORMULA]](img4.gif)
Cygni. The excitation
requirements of these transitions are too high to be satisfied in the
outer envelope of the star, and the emission must originate within
![[FORMULA]](img5.gif)
stellar radii, ie. the molecule must
be forming close to the star. This conclusion is supported by a model
for AGB stars in which molecules including HCN form in a shocked wind
close to the stellar surface.
Key words: stars: AGB and
post-AGB 
stars: circumstellar
matter
stars: individual:
O Cyg
submillimeter
Send offprint requests to: J.Hatchell@umist.ac.uk
Contents
- 1. Introduction
- 2. Observations and results
- 3. Excitation analysis
- 4. Model of the inner wind of Cyg
- 4.1. The chemistry
- 4.2. Model results and discussion
- 5. Conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 2000
Online publication: June 8, 2000
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