The Effect of Binarity on Stellar Rotation Beyond the Reach of Tides.pdf

THE EFFECT OF BINARITY ON STELLAR ROTATION - BEYOND THE REACH OF TIDES1 2,3,4 4 5 Søren Meibom , Robert D. Mathieu , and Keivan G. Stassun ABSTRACT 7 0 0 2 We present a comparison between the rotation period distributions of solar- l u type single stars and primary stars in close binaries (0.1 AU a 5 AU) J in the young (∼ 150 Myr) open cluster M35 (NGC 2168). We find that the 7 primary stars in the close binaries rotate faster than the single stars, on average. ] h The differences in the means and medians between the period distributions are p- statistically significant at the 99.9% level or higher. The faster rotation among o the primary stars in close binaries is not due to tidal synchronization as tidally r t evolved stars are excluded from the comparison. We discuss this result in the s a context of different early-evolution accretion processes and star-disk interactions [ 1 for single stars and stars in close binaries. v 7 8 Subject headings: clusters: open, stars: spectroscopic binaries, stellar rotation, 0 stellar accretion, star-disk interactions 1 . 7 0 7 0 1. INTRODUCTION : v i The rotational properties of young low-mass ( 2 M⊙ ) stars challenge our understanding X r of their angular momentum evolution, and specifically of the physical mechanisms, internal a and external, that control transport of angular momentum. The importance of determin- ing these processes is underscored by the observed loss of a