Optimizing the Resolution of Hydrodynamic Simulations for MCRaT Radiative Transfer Calculations

Theoretical understanding of Gamma Ray Bursts (GRBs) has advanced considerably over the past decades with the aid of new computational tools and techniques. The Monte Carlo Radiation Transfer (MCRaT) code predicts the electromagnetic signature of simulated GRBs by conducting photon scatterings within a jet with a structure calculated with the PLUTO hydrodynamics code. The PLUTO code uses Adaptive Mesh Refinement (AMR) to focus computational efforts on the portion of the grid that contains the simulated jet. Reducing the resolution in the jet would also decrease computational time. However, the effects that a decreased resolution would have on the post-processing radiative transfer results have not yet been quantified. Here, we used MCRaT to analyze the radiation from a spherical outflow and a hydrodynamically simulated jet profile. We show how decreasing both the spatial and temporal resolutions affect the virtual observations of the MCRaT code. We find that changing the grid refinement level changes the hydrodynamic properties of the medium, such as temperature and density, directly affecting the MCRaT mock observable peak energy and luminosity. We also find that decreasing the temporal resolution, lowering the simulation framerate, artificially increases the high energy slope of the mock observable spectrum, increasing then both the spectral peak energy and the luminosity. Our results allow us to understand how decreased hydrodynamic temporal and spatial grid resolution will affect the results of post-processing radiative transfer calculations, permitting us to optimize our computational resources and runtimes.