Variability of the H₂O maser associated with the Mira variable RS Virginis

¹ Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro No. 1, Apdo Postal 51 y 216, 72840 Tonantzintla, Puebla, México
² Sternberg Astronomical Institute, 13 Universitetskij prospekt, Moscow 119899, 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

Corresponding author: E. E. Lekht, lekht@inaoep.mx; mend@inaoep.mx

Received: 12 April 2001
Accepted: 2 July 2001

Abstract

The results of observations of the H₂O maser emission ( cm) of the Mira-type variable star RS Vir are presented. The observations were carried out in 1981-2001 () on the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory (Russia). The variability curve of the H₂O maser emission integrated flux F_int(H₂O) of RS Vir correlates with its visual light curve with some phase delay (P is the star's period). The delay variations seem to be periodic at a timescale of 19-20 years ("superperiod" of the maser variations). If the variability of the H₂O maser RS Vir is caused by periodic action of pulsation-driven shock waves, the shock travel time from the photosphere to the inner boundary of the H₂O maser shell can be as long as (3-5)P. Another explanation is that maser variations may be connected with changing gas density in the masering region of the circumstellar envelope. In particular, long-term maser variations (the "superperiod" ) may be caused by changing mass loss rate .