The lifetime of r cassiopeia's sio maser features

Maser spectra of the long period variable star R Cassiopeia (R Cas) have been observed over approximately four stellar periods in the silicon monoxide v / 1 and v / 2, J / 1 - 0 transition. The linear polarization characteristics of the spectra have been determined. The lifetimes and beginning and ending phases of 43 maser features have been extracted from Gaussian fits to the polarized spectra. It has been proposed that the maser emissions of long-period variables are affected by the passage of a shock wave through the circumstellar region in which the masers originate. The proposed shock passage produces a fading or absence of the emission by phase 0.4 (for v = 1 and v = 2). Our study found that five SiO maser features went out of existence between phases 0.3 and 0.4 for v = 1 and v = 2 (total number of features: 19 for v = 1, 24 for v = 2). In no other phase interval did more than three features go out of existence. This result is in accordance with the above proposition.