Time variations of the ON2 water maser spectrum during 1981-1995

¹ Instituto Nacional de Astrofisica, Optica y Electronica, Apartado Postal 51 y 216, Puebla, Pue., Z.P. 72000, Mexico
² Sternberg Astronomical Institute, Universitetsky prospect 13, 19899, Moscow, Russia

Send offprint request to: J.E. Mendoza-Torres

Received: 3 January 1996
Accepted: 6 May 1996

Abstract

Results of observations at 22.2 GHz of the water maser source ON2 carried out at the Pushchino RT-22 radio telescope during 1981-1995 are presented. The long-time regular observations of ON2 show that the time interval between the two high levels of the integrated H₂O flux density is more than 20 years. The flare component of the variability of total flux as well as strong flares of some features were not detected. The emission is concentrated, basically, in two spectrally separated groups of features. The observed anticorrelation of the fluxes of these groups was manifested only in the period of minimum activity of the H₂O maser. It seems that the transition of the maser takes place from the unsaturated state to a partly saturated one and vice versa. The variability of the maser emission has a global character for ON2 and may be caused by non-stationary physical processes at the early stages of stellar evolution.