|Numerical Simulation of Flares in GRB Afterglow Phase
|459, 6th International Conference of Numerical Modeling of Space Plasma Flows (ASTRONUM 2011)
|Meliani, Z.; Vlasis, A.; Keppens, R.
|We investigate numerically the various evolutionary phases in the interaction of relativistic shells with its surrounding cold interstellar medium (ISM)
and shell-shell interaction. We do this for 1D. This is relevant for gamma-ray bursts (GRBs) and the observed flares, and we demonstrate that, thanks to the
AMR strategy, we resolve the internal structure of the shocked shell and ISM matter and shell-shell matter, which will leave its imprint on the GRB afterglow.
Also, we perform high resolution numerical simulations of late collisions between two ultra-relativistic shells in order to explore the flares in the afterglow
phase of GRB. We examine the case where a cold uniform shell collides with a self-similar Blandford and McKee shell in a constant density environment and
consider cases with different Lorentz factor and energy for the uniform shell. We produce the corresponding on-axis light curves and emission images for
the afterglow phase and examine the occurrence of optical and radio flares assuming a spherical explosion and a hard-edged jet scenario. For our
simulations we use the Adaptive Mesh Refinement version of the Versatile Advection Code (AMRVAC) coupled to a linear radiative transfer code to
calculate synchrotron emission. We find steeply rising flare like behavior for small jet opening angles and more gradual rebrightenings for large
opening angles. Synchrotron self-absorption is found to strongly influence the onset and shape of the radio flare.