Evidence of stellar-driven outflows from the classical T Tauri star RY Tau

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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 velocity of the wind. The repeated observations of the S III] and C III] lines show a lack of changes with time on the blue side of the profile ( dominated by the wind contribution). Very high temperature plasma (log T-e = 4.8) is detected at densities of 9.5 <= log n(e) (cm(-3)) <= 10.2 associated with the wind. The emitting volumes are similar to(0.35 R-.)(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 contributions of several outflows from atmospheric open-field structures like those observed in the Sun.