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University of Tennessee | Department of Physics and Astronomy | Theoretical Astrophysic Group

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2D/3D Ray-by-Ray Neutrino Radiation Hydrodynamics with CHIMERA

Our current tool for 2D and 3D supernova simulations is the CHIMERA code. Developed by the CHIMERA team including Steve Bruenn (FAU), John Blondin (NCSU) & Pedro Marronetti (FAU), and UT/ORNL group members Raph Hix, Eric Lentz, Bronson Messer and Tony Mezzacappa, the CHIMERA code employs “ray-by-ray” (RBR) neutrino transport, using Bruenn’s multi-group flux limited diffusion (MGFLD) code, coupled to the Blondin's MVH-3 hydrodynamics code and Hix’s XNet nuclear reaction network. In the ray-by-ray approximation to multidimensional supernova modeling, radial neutrino transport is included, but not lateral transport. In spherical symmetry, all rays are the same. In multiD, they are not. While a stepping-stone to simulations with more complete 2D/3D transport, the inclusion of multi-frequency ray-by-ray neutrino transport marks a significant advance in realism in 2D/3D models.

First series of 2D Studies in Supernova Progenitor Mass

Our first set (Series A) of well resolved 2D simulations with 256 angular rays and 256 radial zones four different stellar progenitors (12, 15, 20 and 25 solar masses) was reported in Bruenn et al. (2009). Unlike earlier, low-resolution, CHIMERA models using spectral neutrino transport, we see successful explosions across the range of progenitors, caused by a mix of neutrino heating and large scale hydrodynamic instability driven by the standing accretion shock instability (SASI). Gravitational wave signals from these models were reported in Yakunin et al. (2010) and available for download here.

Updated 2D Study of Supernova Progenitor Mass

We are currently computing an updated set of 2D supernova models (Series B) for the same 12, 15, 20, and 25 solar mass progenitors at 256 angular rays, but now with 512 radial zones and several updates to the input physics and CHIMERA code. Results from this series of models are available here.

Pathfinding 3D Studies

To follow-up the success of our 2D studies, we undertook the first 3D core collapse supernova simulation using spectral neutrino transport. At moderate resolution (76 latitudinal zones, 152 longitudinal zones and 304 radial zones) and starting from a 15 solar mass progenitor, this model is currently being run on 11552 processors on the Jaguar computer at NCCS. This simulation evolved from bounce to 140 milliseconds after bounce, where the first signs of neutrino-driven convection were evident. It was reported in Bruenn et al. (2009).

Our current work in 3D uses the the axis-free “Yin-Yang” grid and we look forward to reporting our results in the near future.