出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present multi-epoch total intensity images of 43 GHz, v=1, J=1-0 SiO maser emission toward the Mira variable R Cas. These data were taken as part of a more extensive programme of observations of other stars. In total we have 23 epochs of data for R Cas. Data were recorded at each VLBA antenna in dual-circular polarization in two 4 MHz windows, each digitally sampled at the full Nyquist rate of 8 Mbps in 1-bit quantization at approximate monthly sampling over an optical pulsation phase range of ϕ = 0.158 to ϕ = 1.78. These maps show a ring-like distribution of the maser features in the shell which is assumed to be centered on the star at a distance of 1.9→2.3 times the radius of star (R*) from the star's centre. It is clear from this image that the maser emission is significantly extended around the star. At some epochs a faint outer arc can be seen at 2.2 R*. The intensity of the emission waxes and wanes during the stellar phase. Some maser features are seen infalling as well as out flowing. We are attempting to reconstruct the 3-D velocity field and comparing the result with models of Gray et. al. 2009.
