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Issue A&A
Volume 447, Number 3, March I 2006
Page(s) 949 - 962
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20053609



A&A 447, 949-962 (2006)
DOI: 10.1051/0004-6361:20053609

A self-consistent model of a 22 GHz water maser in a dusty environment near late-type stars

N. Babkovskaia and J. Poutanen

Astronomy Division, PO Box 3000, 90014 University of Oulu, Finland
    e-mail: [natalia.babkovskaia;juri.poutanen]@oulu.fi

(Received 9 June 2005 / Accepted 5 October 2005 )

Abstract
We study the conditions for operation of the 22 GHz ortho-water maser in a dusty medium near late-type stars. The main physical processes, such as exchange of energy between dust and gas in the radiation field of a star, radiative cooling by water molecules and pumping of water masers are described self-consistently. We show that the presence of dust grains of various types (or of one type with size distribution) strongly affects the maser action. The pumping mechanism based on the presence of the dust of different optical properties is able to explain water masers in the silicate carbon star V778 Cyg. However, the masers in the winds from asymptotic giant branch stars require an additional source of heating, for instance due to the dust drift through the gas.


Key words: masers -- radio lines: general -- stars: AGB and post-AGB -- stars: late-type -- methods: numerical -- dust, extinction

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© ESO 2006


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