  The Schwarzschild potential, defined as U(r)=-A/r-B/r^3, where r is the
distance between two mass points and A,B>0, models astrophysical and stellar
dynamics systems in a classical context. In this paper we present a qualitative
study of a three mass point system with mutual Schwarzschild interaction where
the motion is restricted to isosceles configurations at all times. We retrieve
the relative equilibria and provide the energy-momentum diagram. We further
employ appropriate regularization transformations to analyse the behaviour of
the flow near triple collision.
  We emphasize the distinct features of the Schwarzschild model when compared
to its Newtonian counterpart. We prove that, in contrast to the Newtonian case,
on any level of energy the measure of the set on initial conditions leading to
triple collision is positive. Further, whereas in the Newtonian problem triple
collision is asymptotically reached only for zero angular momentum, in the
Schwarzschild problem the triple collision is possible for non-zero total
angular momenta (e.g., when two of the mass points spin infinitely many times
around the centre of mass). This phenomenon is known in celestial mechanics as
the "black-hole effect" and it is understood as an analogue in the classical
context of the behaviour near a Schwarzschild black hole. Also, while in the
Newtonian problem all triple collision orbits are necessarily homothetic, in
the Schwarzschild problem this is not necessarily true. In fact, in the
Schwarzschild problem there exist triple collision orbits which are neither
homothetic, nor homographic.
