  Gamma-ray burst afterglow flares and rebrightenings of the optical and X-ray
light curve have been attributed to both late time inner engine activity and
density changes in the medium surrounding the burster. To test the latter, we
study the encounter between the relativistic blast wave from a gamma-ray
burster and a stellar wind termination shock. The blast wave is simulated using
a high performance adaptive mesh relativistic hydrodynamics code, AMRVAC, and
the synchrotron emission is analyzed in detail with a separate radiation code.
We find no bump in the resulting light curve, not even for very high density
jumps. Furthermore, by analyzing the contributions from the different shock
wave regions we are able to establish that it is essential to resolve the blast
wave structure in order to make qualitatively correct predictions on the
observed output and that the contribution from the reverse shock region will
not stand out, even when the magnetic field is increased in this region by
repeated shocks. This study resolves a controversy in recent literature.
