Stellar rotation bifurcation caused by tidal locking in the open cluster
  NGC 2287?
  We present a detailed analysis of the projected stellar rotational velocities
of the well-separated double main sequence (MS) in the young, $\sim200$Myr-old
Milky Way open cluster NGC 2287 and suggest that stellar rotation may drive the
split MSs in NGC 2287. We find that the observed distribution of projected
stellar rotation velocities could result from a dichotomous distribution of
stellar rotation rates. We discuss whether our observations may reflect the
effects of tidal locking affecting a fraction of the cluster's member stars in
stellar binary systems. The slow rotators are likely stars that initially
rotated rapidly but subsequently slowed down through tidal locking induced by
low-mass-ratio binary systems. However, the cluster may have a much larger
population of short-period binaries than is usually seen in the literature,
with relatively low secondary masses.
