The 43GHz SiO maser in the circumstellar envelope of the AGB star R
  Cassiopeiae
  We present multi-epoch, total intensity, high-resolution images of 43GHz,
v=1, J=1-0 SiO maser emission toward the Mira variable R Cas. In total we have
23 epochs of data for R Cas at approximate monthly intervals over an optical
pulsation phase range from 0.158 to 1.78. These maps show a ring-like
distribution of the maser features in a shell, which is assumed to be centred
on the star at a radius of 1.6 to 2.3 times the stellar radii. It is clear from
these images that the maser emission is significantly extended around the star.
At some epochs a faint outer arc can be seen at 2.2 stellar radii. The
intensity of the emission waxes and wanes during the stellar phase. Some maser
features are seen infalling as well as outflowing. We have made initial
comparisons of our data with models by Gray et. al. (2009).
