  We model the physical behaviour at the surface of a relativistic radiating
star in the strong gravity limit. The spacetime in the interior is taken to be
spherically symmetrical and shear-free. The heat conduction in the interior of
the star is governed by the geodesic motion of fluid particles and a
nonvanishing radially directed heat flux. The local atmosphere in the exterior
region is a two-component system consisting of standard pressureless (null)
radiation and an additional null fluid with nonzero pressure and constant
energy density. We analyse the generalised junction condition for the matter
and gravitational variables on the stellar surface and generate an exact
solution. We investigate the effect of the exterior energy density on the
temporal evolution of the radiating fluid pressure, luminosty, gravitational
redshift and mass flow at the boundary of the star. The influence of the
density on the rate of gravitational collapse is also probed and the strong,
dominant and weak energy conditions are also tested. We show that the presence
of the additional null fluid has a significant effect on the dynamical
evolution of the star.
