NOAO >   Observing Info >   Approved Programs >   2004B-0283

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Proposal Information for 2004B-0283


PI: Keivan Stassun, Vanderbilt University, keivan.stassun@vanderbilt.edu
Address: Physics Department, VU Station B 1807, Nashville, TN 37235, USA

CoI: Robert Mathieu, University of Wisconsin
CoI: Soeren Meibom, University of Wisconsin

Title: Angular Momentum Evolution of Young, Low-Mass Stars: The Role of Stellar Multiplicity

Abstract: The evolution of stellar angular momentum during the pre-main- sequence (PMS) phase remains a fundamental challenge to our understanding of star formation and early stellar evolution. To date, efforts to model the observed evolution of PMS angular momentum have essentially treated this as a single-star problem even though most stars reside in binary systems. \bf The goal of this proposal is to study the role of stellar multiplicity in the angular momentum evolution of young, low-mass stars. Of particular interest are the extremely rapidly rotating PMS stars (P_\rm rot < 1 day) recently discovered by us in Orion: Are these in fact single stars rotating close to breakup velocity, or are they tidally locked binaries? More generally, we seek to test theoretical predictions of tidal interactions in young binary systems: Different theoretical treatments make different predictions for the magnitude and time-dependence of rotational synchronization and orbital circularization. We will obtain precise radial-velocity measurements of 50 low-mass pre-main-sequence stars in Orion (1 Myr) for which rotation periods are known. Our objectives are two-fold: (1) Derive spectroscopic orbits for the spectroscopic binaries in this sample, allowing us to test the theoretical predictions of rotational synchronization and orbital circularization; and (2) Determine which, if any, of the ultra-fast rotators in this sample are binaries, allowing us to test the hypothesis that binaries are governing the rapid extremes of PMS angular momentum evolution.


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