Multiepoch VLBA Observations of T Tauri South

In this Letter, we present a series of seven observations of the compact, nonthermal radio source associated with T Tauri South made with the Very Long Baseline Array (VLBA) over the course of 1 year. The emission is found to be composed of a compact structure most certainly originating from the magnetosphere of an underlying pre-main-sequence star and a low brightness extension that may result from reconnection flares at the star-disk interface. The accuracy of the absolute astrometry offered by the VLBA allows us to make very precise determinations of the trigonometric parallax and proper motion of T Tau South. The proper motion derived from our VLBA observations agrees with that measured with the Very Large Array over a similar period to better than 2 mas yr-1, and it is fully consistent with the infrared proper motion of T Tau Sb, the pre-main-sequence M star with which the radio source has traditionally been associated. The parallax, π = 7.07 ± 0.14 mas, corresponds to a distance of 141.5 pc.