Optical and Microwave Spectroscopy of Long-Period Variable Stars
The results of multiwavelength studies (optical spectroscopy, H2O maser line, radio continuum) of a sample of long-period variable stars are presented. For some of the stars studied (R Aql, RR Aql, W Hya, U Ori) the H2O maser emission has been detectable throughout the monitoring interval, for more than 20 years. A comparison of the H2O maser monitoring of these stars with their visual light curves suggests a correlation of their maser and optical brightness. There is a phase lag Aφ ~ 0.1 – 0.4P (P is the star’s variability period) of the H2O maser variations relative to the optical variability. There are also stars (‘transient masers’, R Leo, R Cas, U Aur) that have exhibited short-duration flares in the H2O maser line with several years of no detectable emission between them. The H2O maser flares were preceded by flares of the Hα emission line. The common cause of such sequence of events can be the consecutive impact of a shock wave on different layers of the stellar atmosphere and circumstellar envelope
KeywordsMiras spectroscopy emission lines masers
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