2013 IR&D Annual Report

Capability Development of Type II Supernova Models, 15-R8333

Principal Investigator
Amanda Bayless

Inclusive Dates: 09/17/12 – 01/17/13

Background — An enduring problem in understanding our cosmic origins is to understand the processes by which heavy elements, the building blocks of life and planets, are created and distributed throughout the universe. We now know that many of these heavy elements are created in the final stages of a massive star's life and released into the surrounding environment when the nuclear reactor stellar core explodes as a supernova. These stars were between eight and 100 times the mass of the Sun and release ~ 1051 ergs/s, or about the energy of 1030 atomic bombs. This is enough energy to create heavy elements through neutron fusion and beta decay. Despite our progress in understanding, the mechanisms by which a star explodes and how the elements are distributed are not well understood. The information we have primarily comes from observations and spectra showing the change in brightness over time and the elemental content at the edge of the supernova. These observations do not give us direct information on the internal processes of the explosion or information about the star that exploded, which are crucial for understanding the life cycle of massive stars. A comprehensive model of the explosion is needed to fully understand how and why the most massive stars end their life catastrophically.

Producing a computer model for supernovae that matches observational data is a very difficult problem. Due to limited computational resources, most numerical models incorporate only one or two of the following critical physical laws: magneto-hydrodynamics, radiative transfer, nuclear processes, or atomic transitions. These limitations are accommodated by making basic uniform assumptions about the dynamics, opacities and wavelength dependencies. Nevertheless, these assumptions frequently affect the accuracy of key parameters, such as the energetics of the supernova and the initial mass, radius, etc., of the star. The mass range alone for a star can vary over a magnitude in parameter space, and often there is no a priori information, resulting in an extensive search of parameter space. This search can be months of computing and personnel resources, with no guarantee that the final model fit is a unique solution.

Approach — The proposed solution is to use a modeling code that incorporates all of the critical physics, not just a subset; use a state-of-the-art computational resource required by such a code; and create a database of models from this code, filling a reasonable range of parameter space, to minimize the need for future computational resources. The database of models that will ultimately be created will be quickly searchable, giving an almost immediate, excellent constraint and understanding of supernovae discovered in the future. This database of models will be available publically in the form of a coarse grid in parameter space. The refinement of the model fits using the new code can only occur with SwRI and LANL collaboration.

Accomplishments — The first paper that is a direct result of this effort has been submitted. Four proposals resulted from this work.

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