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Astron. Astrophys. 358, L25-L28 (2000)

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Letter to the Editor

HCN in the inner envelope of [FORMULA] 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


We have detected the [FORMULA] and [FORMULA] transitions of HCN towards the S star [FORMULA] 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] 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

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000