  A numerical solution of Einstein field equations for a spherical symmetric
and stationary system of identical and auto-gravitating particles in phase
transition is presented. The fluid possess a perfect fluid energy momentum
tensor, and the internal interactions of the system are represented by a van
der Walls like equation of state able to describe a first order phase
transition of the type gas-liquid. We find that the space-time curvature, the
radial component of the metric, and the pressure and density show
discontinuities in their radial derivatives in the phase coexistence region.
This region is found to be a spherical surface concentric with the star and the
system can be thought as a foliation of acronal, concentric and isobaric
surfaces in which the coexistence of phases occurs in only one of these
surfaces. This kind of system can be used to represent a star with a high
energy density core and low energy density mantle in hydrodynamic equilibrium.
