  We calculate the evolution of planets undergoing a strong tidal encounter
using smoothed particle hydrodynamics (SPH), for a range of periastron
separations. We find that outside the Roche limit, the evolution of the planet
is well-described by the standard model of linear, non-radial, adiabatic
oscillations. If the planet passes within the Roche limit at periastron,
however, mass can be stripped from it, but in no case do we find enough energy
transferred to the planet to lead to complete disruption. In light of the three
new extrasolar planets discovered with periods shorter than two days, we argue
that the shortest-period cases observed in the period-mass relation may be
explained by a model whereby planets undergo strong tidal encounters with
stars, after either being scattered by dynamical interactions into highly
eccentric orbits, or tidally captured from nearly parabolic orbits. Although
this scenario does provide a natural explanation for the edge found for planets
at twice the Roche limit, it does not explain how such planets will survive the
inevitable expansion that results from energy injection during tidal
circularization.
