MOCCA code for star cluster simulations - VI. Bimodal spatial
  distribution of blue stragglers
  The paper presents an analysis of formation mechanism and properties of
spatial distributions of blue stragglers in evolving globular clusters, based
on numerical simulations done with the MOCCA code. First, there are presented
N-body and MOCCA simulations which try to reproduce the simulations presented
by Ferraro (2012). Then, the agreement between N-body and the MOCCA code is
shown. Finally, we discuss the formation process of the bimodal distribution.
We report that so-called bimodal spatial distribution of blue stragglers is a
very transient feature. It is formed for one snapshot in time and it can easily
vanish in the next one. Moreover, we show that the radius of avoidance proposed
by Ferraro (2012) goes out of sync with the apparent minimum of the bimodal
distribution after about two half-mass relaxation times. This finding creates a
real challenge for the dynamical clock, which uses this radius to determine the
dynamical age of globular clusters. Additionally, the paper discusses a few
important problems concerning the apparent visibilities of the bimodal
distributions which have to be taken into account while studying the spatial
distributions of blue stragglers.
