Unexpected Formation Modes of the First Hard Binary in Core Collapse
  The conventional wisdom for the formation of the first hard binary in core
collapse is that three-body interactions of single stars form many soft
binaries, most of which are quickly destroyed, but eventually one of them
survives. We report on direct N-body simulations to test these ideas, for the
first time. We find that both assumptions are often incorrect: 1) quite a few
three-body interactions produce a hard binary from scratch; 2) and in many
cases there are more than three bodies directly and simultaneously involved in
the production of the first binary. The main reason for the discrepancies is
that the core of a star cluster, at the first deep collapse, contains typically
only five or so stars. Therefore, the homogeneous background assumption, which
still would be reasonable for, say, 25 stars, utterly breaks down. There have
been some speculations in this direction, but we demonstrate this result here
explicitly, for the first time.
