Cool Stars 14 - Submitted Abstract # 242
This version created on 05 October 2006

The effect of binarity on stellar rotation - beyond the reach of tidal
synchronization


Soren Meibom, Harvard-Smithsonian Center for Astrophysics
Robert D. Mathieu, University of Wisconsin - Madison
Keivan G. Stassun, Vanderbilt University

We present a direct comparison between the rotation period
distribution of the primary stars in close binaries (a ~< 5 AU) and
the rotation period distribution of single stars or primary stars in
wider binaries in the young (150  Myr) open cluster M35.  We find that
the primary stars in the close binaries rotate on average faster than
the single stars or primary stars in wide binaries.  The difference in
the means and medians between the two period distributions is
statistically significant at the 99.9% level or higher.  The faster
rotation among the primary stars in the close binaries is not due to
tidal synchronization as synchronized binaries were excluded.  Within
the framework of current models of PMS stellar angular momentum
evolution due to magnetic star-disk interactions, this finding may
suggest that the lifetimes of circumstellar disks in binaries with
semi-major axes less than ~5 AU are shorter than for single stars or
stars in wider binaries.  Such shorter circumstellar disk lifetimes
may be the result of either dynamical disruption or the lack of
replenishment from mass accretion due to the binary companions.

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