The Rotation of Low-Mass Pre-Main-Sequence Stars

Authors:
Robert D. Mathieu

Comments: 10 pages, 5 figures, conference proceedings

Major photometric monitoring campaigns of star-forming regions in the past
decade have provided rich rotation period distributions of pre-main-sequence
stars. The rotation periods span more than an order of magnitude in period,
with most falling between 1 and 10 days. Thus the broad rotation period
distributions found in 100 Myr clusters are already established by an age of 1
Myr. The most rapidly rotating stars are within a factor of 2-3 of their
critical velocities; if angular momentum is conserved as they evolve to the
ZAMS, these stars may come to exceed their critical velocities. Extensive
efforts have been made to find connections between stellar rotation and the
presence of protostellar disks; at best only a weak correlation has been found
in the largest samples. Magnetic disk-locking is a theoretically attractive
mechanism for angular momentum evolution of young stars, but the links between
theoretical predictions and observational evidence remain ambiguous. Detailed
observational and theoretical studies of the magnetospheric environments will
provide better insight into the processes of pre-main-sequence stellar angular
momentum evolution.

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