| Description: | Most evolved stars are pulsating objects. The pulsation leads to a mass loss process which forms a circumstellar envelope. In the innermost region, a very peculiar emission is detected, the SiO MASERS (Microwave Amplification by the Stimulated Emission of Radiation). The figure shows the masing region in the star TXCam observed with the VLBA. The SiO emission consists of ring-like structures composed of multiple and small clumps or spots. This spatial distribution is explained by two mechanisms: how the maser is pumped and how the stellar radiation is amplified. |
