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Issue A&A
Volume 437, Number 1, July I 2005
Page(s) 127 - 133
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20052635



A&A 437, 127-133 (2005)
DOI: 10.1051/0004-6361:20052635

Variability of the H $\mathsf{_2}$O maser associated with the M-supergiant S Persei

E. E. Lekht1, 2, G. M. Rudnitskij2, J. E. Mendoza-Torres1 and A. M. Tolmachev3

1  Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro No. 1, Apdo Postal 51 y 216, 72840 Tonantzintla, Puebla, México
    e-mail: [lekht;mend]@inaoep.mx
2  Sternberg Astronomical Institute, 13 Universitetskij prospekt, Moscow, 119992 Russia
    e-mail: gmr@sai.msu.ru
3  Pushchino Radio Astronomy Observatory, Astrospace Center of the Lebedev Institute of Physics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia
    e-mail: tolm@prao.psn.ru

(Received 3 January 2005 / Accepted 3 February 2005)

Abstract
We present the results from observing the circumstellar maser emission of the M-type supergiant S Per in the 616-523 water-vapour line at 1.35 cm. The observations were carried out in 1981-2002 ( $\rm JD=2\,444\,900$-2 452 480) on the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory, Astrospace Center of the Lebedev Institute of Physics, Russian Academy of Sciences. The H2O spectra obtained represent an unprecedented long, uniform dataset on this star. We discuss the properties of the optical and maser variations of S Per, together with particulars of the available VLBI maps. The close relation between maser and optical variations favors a model in which mass-loss is episodic. Changes observed in the total H2O line flux follow the visual light curve with a delay of 0.01 to 0.5P, where $P\approx 800$ d is the mean light cycle for S Per. The feature at VLSR=-44 km s-1 flared in July 1988, which seemed to be the response of the maser to an unusually bright optical maximum. The position of the -44-km s-1 feature on the VLBI maps coincides with the direction toward the optical stellar disc, which can be explained by amplification of enhanced stellar continuum by the H2O line.


Key words: stars: AGB and post-AGB -- circumstellar matter -- stars: mass-loss -- stars: supergiants -- masers -- stars: late-type

SIMBAD Objects in preparation



© ESO 2005


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