MULTIPLE DUST SHELLS AND MOTIONS AROUND IK TAURI AS SEEN BY INFRARED INTERFEROMETRY

A visibility curve of IK Tau has been measured with the ISI, an 11 mu m stellar interferometer, over a period of several years. Time variati ons in 11 mu m flux were also measured. The results indicate an approx imately periodic distribution of dust shells around the star, with she lls separated by 200-250 mas and a diameter of about 200 mas for the i nnermost shell. Some shell motion has been detected, and if velocities are the same as those measured for CO gas and OH masers, the motion i mplies that the distance to IK Tau is about 265 pc and that shells hav e been emitted at times separated by about 12 yr, which is considerabl y longer than the star's luminosity period of 470 days.