R. Köhler, M. Kasper, T. M. Herbst, T. Ratzka, and G. H.-M. Bertrang
Context. Aims: We present new astrometric measurements of the components in the T Tauri system and derive new orbits and masses.
Methods: T Tauri was observed during the science verification time of the new extreme adaptive optics facility SPHERE at the VLT. We combine the new positions with recalibrated NACO-measurements and data from the literature. Model fits for the orbits of T Tau Sa and Sb around each other and around T Tau N yield orbital elements and individual masses of the stars Sa and Sb.
Results: Our new orbit for T Tau Sa/Sb is in good agreement with other recent results, which indicates that enough of the orbit has been observed for a reliable fit. The total mass of T Tau S is 2.65 ± 0.11 M⊙. The mass ratio MSb:MSa is 0.25 ± 0.03, which yields individual masses of MSa = 2.12 ± 0.10 M⊙ and MSb = 0.53 ± 0.06 M⊙. If our current knowledge of the orbital motions is used to compute the position of the southern radio source in the T Tauri system, then we find no evidence of the proposed dramatic change in its path.