Spatial mixing of binary stars in multiple-population globular clusters
  We present the results of a study aimed at investigating the effects of
dynamical evolution on the spatial distribution and mixing of primordial binary
stars in multiple-population globular clusters.
  Multiple stellar population formation models predict that second-generation
(SG) stars form segregated in the inner regions of a more extended
first-generation (FG) cluster. Our study, based on the results of a survey of
N-body simulations, shows that the spatial mixing process for binary stars is
more complex than that of single stars since additional processes such as
binary ionization, recoil and ejection following binary-single and
binary-binary interactions play a key role in determining the spatial
distribution of the population of surviving binaries. The efficiency and
relative importance of these additional effects depends on the binary binding
energy and determines the timescale of the spatial mixing of FG and SG
binaries. Our simulations illustrate the role of ionization, recoil and
ejection combined with the effects of mass segregation driven by two-body
relaxation and show that the complex interplay of all these processes results
in a significant extension of the time needed for the complete spatial mixing
of FG and SG binaries compared to that of single stars. Clusters in which FG
and SG single stars have already reached complete spatial mixing might be
characterized by a significant radial gradient in the ratio of the FG-to-SG
binary fraction. The implications of the delayed mixing of FG and SG binaries
for the differences between the kinematics of the two populations are
discussed.
