AAS 205th Meeting, 9-13 January 2005
Session 107 Binary Stars Including Theory and Activity
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall

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[107.02] Observations of Tidal Synchronization in Detached Solar-Type Binary Stars.

S. Meibom, R. D. Mathieu (UW Madison), K. Stassun (Vanderbilt University)

Tidal forces in close detached binary stars drive the exchange of angular momentum between the stars and their orbital motion. Depending on the strength of the tidal interactions the stars in a binary system will synchronize their rotation with the orbital motion. Theoretical models predict that the rate of synchronization depends sensitively on the separation of the two stars and on the mechanism for dissipation of kinetic energy into heat within the stars. The amount of observational data suitable for testing the rate of tidal synchronization in late-type close binaries is sparse. Most of the observational work on synchronization in close binaries has concentrated on early-type stars with radiative envelopes where the mechanism for tidal dissipation is different.

We present observational results on tidal synchronization in detached solar-type binary stars in the open clusters M35 (NGC2168; ~ 150 Myr) and M34 (NGC1039; ~ 250 Myr). M35 and M34 provide populations of close late-type binaries with ages that make them attractive observational tests of models of tidal synchronization during the early main-sequence phase. A combined dataset of stellar rotation periods from time-series photometry and binary orbital periods and eccentricities from time-series spectroscopy enables us to determine the angular rotation velocity of the primary star and the orbital angular velocity at periastron. Comparison of the stellar and orbital angular velocities provides important constraints on the predicted level of synchronization in binary stars as a function of period.

This work has been supported by NSF grant AST-0098417 and by a Ph.D fellowship from the Danish Research Agency (Forskningstyrelsen) to S.M

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