Rotational and radial velocities of T Tauri stars

Rotational and radial velocities are reported for 50 T Tauri stars in the Taurus-Auriga and Orion complexes. The results indicate that most T Tauri stars rotate at rates an order of magnitude or more below breakup velocity, with high-mass stars exhibiting larger rotational velocities than low-mass stars. Large amounts of angular momentum are lost within the first 100,000 years after the end of protostellar accretion, while low-mass T Tauri stars lose at most about three-fourths of their angular momentum during their visible premain sequence evolution. There is evidence that the rotational velocity distribution for T Tauri stars with a common radius is peaked at low rotation values, and has a high-velocity tail. 68 references.