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Astron. Astrophys. 322, 938-942 (1997)

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Explanation of [FORMULA] SiO, [FORMULA] SiO and high-v [FORMULA] SiO maser emission

E. González-Alfonsoand J. Cernicharo 1, 2, 2, 3

1 Universidad de Alcalá de Henares, Departamento de Física, Campus Universitario, E-28871 Alcalá de Henares, Madrid, Spain
2 Observatorio Astronómico Nacional (OAN), E-28800 Alcalá de Henares, Madrid, Spain
3 CSIC, IEM, Dpto. Física Molecular, Serrano 123, E-28006 Madrid, Spain

Received 7 May 1996 / Accepted 2 December 1996

Abstract

We have developed a non-local radiative transfer code to study the effects of line overlaps between different molecular species on the emergent line intensities from interstellar and circumstellar clouds. The numerical method solves the transfer of radiation and the statistical equilibrium populations for the different molecules simultaneously, and allows a direct comparison between the intensities calculated when overlaps are included/ignored in the models. We have applied the code to explain the maser emission in the rotational lines of 29 SiO, 30 SiO and high-v ([FORMULA]) 28 SiO observed toward oxygen-rich circumstellar envelopes. The model calculations show that the pumping mechanism for most of these lines is dominated by infrared line overlaps between 28 SiO, 29 SiO and 30 SiO.

Key words: masers – radiative transfer – stars: AGB – circumstellar matter – ISM: clouds; molecules

Send offprint requests to: E. González-Alfonso

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© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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