Gamma-ray Bursts in Inhomogeneous Interstellar Media

Gamma-ray bursts (GRBs) are among the most luminous electromagnetic phenomena in the known universe, but there is still much unknown about them. In particular, their circumstellar environments are likely much more complicated than a simple massive-star wind-density profile, as is commonly assumed. Long GRBs show late time flares in their optical and X-ray light curves that may be a reflection of this rich environment. Using relativistic hydrodynamics simulations, we study a family of initial data with a relativistic blast wave encountering a dense circumstellar shell of matter, similar to what might be generated by an aging star expelling the outer layers of its atmosphere. We test the possibility that some of the late time curve variability may result from these interactions and characterize the profiles of the reverse shocks.