Gamma-ray Bursts in Inhomogeneous Interstellar Media

Gamma-ray bursts (GRBs) are some of the most energetic phenomena in the known universe, but some of the physics surrounding these events remains poorly understood. In particular, light curves associated with long GRBs often demonstrate a high degree of variability. While variations in these spectra could result from the dynamics of the central engine, interactions of the blast wave with an inhomogeneous interstellar medium can also play a role. We investigate this latter effect by studying the collision of relativistic blast waves with dense stellar ejecta and estimate the effect on an observed light curve. We solve the relativistic fluid equations for a blast configuration and model the inhomogeneity as shells surrounding the star, such as might occur when an aging star expels its outer layers. We discuss the numerical algorithms and present preliminary results from our simulations.