Spectroscopic Binaries in the Orion Nebula Cluster and NGC 2264
  We examine the spectroscopic binary population for two massive nearby regions
of clustered star formation, the Orion Nebula Cluster and NGC 2264,
supplementing the data presented by Tobin et al. (2009, 2015) with more recent
observations and more extensive analysis. The inferred multiplicity fraction up
to 10 AU based on these observations is $5.3\pm 1.2$% for NGC 2264 and $5.8\pm
1.1$% for the ONC; they are consistent with the distribution of binaries in the
field in the relevant parameter range. Eight of the multiple systems in the
sample have enough epochs to make an initial fit for the orbital parameters.
Two of these sources are double-lined spectroscopic binaries; for them we
determine the mass ratio. Our reanalysis of the distribution of stellar radial
velocities towards these clusters presents a significantly better agreement
between stellar and gas kinematics than was previously thought.
