Memorie della Societa Astronomica Italiana vol:82 pages:137-140
workshop MPI location:Bonn, Germany date:7-8 april 2010
Abstract. Strong optical and X-Ray flares often appear in the afterglow phase of Gamma-Ray Bursts (GRBs). We perform high resolution numerical simulations of late collisions
between two ultra-relativistic shells in order to explore these events. Such consecutive shells can be formed due to the variability in the central source of a GRB. We examine the case where a cold uniform shell collides with a self similar relativistic, shocked shell (Blandford & McKee 1976) in a constant density environment. We produce the corresponding light curves for the afterglow phase and examine the occurrence and chromaticity of optical and
radio flares assuming dierent opening angles. We conclude that occurrence of optical and radio flares is possible for small opening angles of the jet. For our simulations we use the Adaptive Mesh Refinement version of the Versatile Advection Code (Keppens et al. 2003; Meliani et al. 2008) while the synchrotron radiation has been calculated with the method introduced in Van Eerten & Wijers (2009).