POSTER PAPER 4.03
Angular Momentum Evolution of Stars in the Orion Nebula Cluster
Jeremy Tinker, Marc Pinsonneault, and Donald Terndrup
Institute: Department of Astronomy, Ohio State University
Contact Email: tinker@astronomy.ohio-state.edu
Abstract:
We present theoretical models of stellar angular momentum evolution
from the Orion Nebula Cluster (ONC) to the Pleiades and the Hyades.
The observed periods, masses and ages of ONC stars in the range
0.2--0.5 MSun, and the loss properties inferred from the Pleiades
and Hyades stars, are used as the initial conditions for stellar
evolution models. We then use these models to estimate the distribution of
rotational velocities for the ONC stars at the age of the Pleiades
(120 Myr). The modeled ONC and observed Pleiades distributions of
rotation rates are not consistent if only stellar winds are
included. In order to reconcile the observed loss of angular momentum
between these two clusters, an extrinsic loss mechanism such as
protostar-accretion disk interaction is required. Our model, which
evolves the ONC stars with a mass dependent saturation threshold
normalized such that Omegacrit = 5.4 OmegaSun at 0.5 MSun, and
which includes a distribution of disk lifetimes that is uniform over
the range 0--6 Myr, is consistent with the Pleiades data. This model
for disk-locking lifetimes is also consistent with inferred disk
lifetimes from the percentage of stars with infrared excesses observed
in young clusters. Different models, using a variety of initial period
distributions and different maximum disk lifetimes, are also compared
to the Pleiades. For disk-locking models that use the ONC period
distribution and a uniform distribution of disk lifetimes over the
range 0 to Tmax, the acceptable range of the maximum lifetime
is 3.5 < Tmax < 8.5 Myr.
Index Keywords:
Previous: Granzer
Next: Briceno
Up: Poster Index
Up: Top Index
Manuscript submitted: 2001-Sep-17
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.