Evidence of Stellar-driven Outflows from the Classical T Tauri Star RY Tau

Abstract

RY Tau is a rapidly rotating Classical T Tauri star observed close to edge-on. The combination of new HST/STIS observations obtained in 2001 with HST/GHRS Archive data from 1993 has allowed us to get, for the first time, information on the thermal structure and the velocity law of the wind. The repeated observations of the Si III] and C III] lines show a lack of changes with time in the blue side of the profile(dominated by the wind contribution). Very high temperature plasma (log Te = 4.8) is detected at densities of 9.5<log ne(cm3)< 10.2 associated with the wind. The emitting volumes are about (0.35Ro)^3 suggesting a stellar origin. The wind kinematics derived from the profiles (Si III], C III] and [O II]) does not satisfy the theoretical predictions of MHD centrifugally driven disk winds. The profiles' asymmetry, large velocity dispersions and small variability as well as the small emitting volumes are best explained if the wind is produced by the contribution of several outflows from atmospheric open field structures as those observed in the Sun.