A New General Relativistic, Magnetohydrodynamics, Radiation Transport Code For Dynamical Spacetimes

We describe our new radiative transport module that we implemented in the Illinois GRMHD code. The module employs the general relativistic truncated moment ("M1") formalism, which uses an analytic expression to close the radiation moment equations and smoothly interpolates between optically thin and thick limits. We tested the scheme by simulating thermal Oppenheimer-Synder collapse to a black hole and find we can reliably reproduce the results in previous studies that could only treat transport in the optically thick interior. However, our M1 scheme can also track the emitted radiation into the optically thin exterior and correctly determines the emission as viewed by a distant observer. We then employ our code to treat the full GRMHD-neutrino transport evolution of a merging binary neutron star system. Two versions are considered: a "simple" one that evolves a single neutrino species (electron anti-neutrino) and considers only charged-current processes and another "complete" one that evolves all three species (electron neutrino, electron anti-neutrino, and heavy-lepton neutrino) with all relevant interactions. Preliminary results will be presented.