Variable Asymmetry of the Circumstellar Envelope in IK Tauri Traced by SiO Maser Emission

We observed the SiO ($v=1$ and $v=2$, $J=$ 1-0) maser emissions toward the Mira variable IK Tauri (IK Tau, NML Tau, IRC+10050) over nine epochs from 2003 November to 2005 April using the VLBI Exploration of Radio Astrometry (VERA) telescope array. We found that the SiO maser distributions around IK Tau are highly variable, depending on the stellar pulsation phase. The velocity structures were comp...