Rotational Evolution and Radii of Young Sun-like Stars in NGC 2264

A major goal in astronomy is understanding the formation and evolution of our Solar System and that of other Sun-like stars and planetary systems. Investigating the angular momentum evolution of T Tauri stars provides important insight into the interactions between Sun-like stars and their protoplanetary disks and the timescales that govern disk dissipation and planet formation. We present projected rotational velocities (v sin(i) values) of 220 T Tauri stars in the open cluster NGC 2264, measured using high-dispersion spectra from the WIYN 3.5m telescope’s Hydra instrument. We combine these with literature values of temperature, rotation period, luminosity, disk classification, and binarity. We find some evidence that weak-lined T Tauri stars may rotate faster than their classical T Tauri counterparts with accreting disks and that stars in binary systems may rotate faster than single stars. We also use a maximum likelihood modeling technique to compare the projected stellar radii of our sample stars to the radii predicted by stellar evolution models. We find that starspot-free models tend to underestimate the radii of the PMS stars, while models that include starspot coverage are more successful. Our study of NGC 2264 serves as a pilot study for analysis methods that will be applied to four other clusters ranging in age from 1 to 15 Myr, the timescale over which the protoplanetary disk dissipates and planetary systems begin to form.