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D. A. Boboltz (USNO), P. J. Diamond (Jodrell Bank)
We report on VLBI observations of the v=1,J=1-0, 43-GHz SiO masers towards the Mira variable IK Tauri (IK Tau) using the Very Long Baseline Array (VLBA). The SiO maser emission spans an L.S.R. velocity range from approximately 29 km s-1 to 41 km s-1. The images resulting from these observations show that the SiO masers are distributed in an axisymmetric ring roughly 29 \times 16 mas at a position angle of ~59 deg. The semimajor axis of the elliptical distribution also provides an axis of symmetry for the velocity structure of SiO masers with blue-shifted features (~29-35 km s-1) lying to the northwest and red-shifted features (~35-41 km s-1) lying to the southeast. This velocity distribution may be indicative of rotation in the circumstellar envelope of IK Tau at the distance of the SiO maser emission.