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Session 49 - Young Stellar Objects.
Display session, Tuesday, January 14
Metropolitan Ballroom,
We report initial results of a study aimed at an empirical definition of the angular momentum evolution of low mass (M < 0.5 M_ødot) stars in NGC 2264. These stars are intermediate in age between the "stellar birthline" and the zero age main sequence (ZAMS). We have measured rotation periods from CCD imaging observations of starspot-modulated light curves for a large proper-motion-selected sample of pre-main sequence (PMS) stars in NGC 2264. Our deep VRIJHK photometric survey (reported here for the first time) indicates that this sample: (a) comprises PMS stars with ages 1 < t < 15 Myr, and (b) contains objects still surrounded by circumstellar accretion disks, and objects which lack disks. It is thus ideally suited for testing whether, as hypothesized, (a) accretion disks regulate PMS stars of a given mass to an approximately constant period as they contract toward the ZAMS; and (b) whether the rotational evolution of low mass stars which lack disks primarily reflects contraction as these PMS objects approach the ZAMS, or whether angular momentum loss is significant.
