The 43GHz SiO maser in the circumstellar envelope of the AGB star R Cassiopeiae

TL;DR

This study provides high-resolution, multi-epoch images of 43GHz SiO maser emission around the Mira variable R Cas, revealing a dynamic, ring-like shell structure with variable intensity and motion, offering insights into circumstellar environments.

Contribution

First multi-epoch, high-resolution imaging of SiO masers around R Cas, showing detailed shell structure and maser dynamics over stellar pulsation phases.

Findings

Maser features form a ring-like shell around the star.

Maser emission intensity varies with stellar phase.

Evidence of both infalling and outflowing maser features.

Abstract

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).