Tinker, Jeremy

Contact Email: tinker@astronomy.ohio-state.edu
Institute: Department of Astronomy, Ohio State University
First Coauthor: Marc Pinsonneault
Institute: Ohio State University
Second Coauthor: Donald Terndrup
Institute: Ohio State University
Subject Area: Stellar Evolution
Waveband: Infrared
Technique: Computational Astrophysics
Presentation:
Title: Angular Momentum Evolution of Stars in the Orion Nebula Cluster
Abstract: We present theoretical models of stellar angular momentum evolution from the Orion Nebula Cluster (ONC) to the Pleiades and the Hyades. We demonstrate that observations of the Pleiades and Hyades place tight constraints on the angular momentum loss rate from stellar winds. The observed periods, masses and ages of ONC stars in the range 0.2-0.5 M$_\odot$, and the loss properties inferred from the Pleiades and Hyades stars, are then used to test the initial conditions for stellar evolution models. We 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 saturation threshold of $\omega_{crit} = 5.4 \omega_\odot$at 0.5 M$_\odot$, and which includes a distribution of disk lifetimes that is uniform over the range 0-6 Myr is consistent with the Pleiades. This model for disk-locking lifetimes is also consistent with inferred disk lifetimes from the presence 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 a uniform distribution of disk lifetimes from [0, $\tau_{max}$], the acceptable range of the maximum lifetime is $3.0 < \tau_{max} < 8.5$Myr. We also use the ONC period data combined with infrared excess data to test this model directly on the pre-main-sequence. At present, the sample of data is not large enough to make strong conlusions based upon this test.