The Final Hour of a Massive Star: Silicon Shell Burning and the Subsequent Supernova

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

The final stage of life for a massive star (larger than about nine times the mass of the Sun) is the nuclear fusion ("burning") of silicon (SiSB) to create iron in a shell around an inert iron core, increasing the mass of the iron core.  This stage can last up to an hour until growth of the iron core triggers its collapse to a compact and dense neutron star (NS) surrounded by accreting material. Subatomic particles called neutrinos emitted by the new NS heat the material and drive it out in a shock front through the surrounding star, generating a supernova explosion that delivers newly made elements into the interstellar medium of the galaxy. A research team at the University of Tennessee, Knoxville, will follow multidimensional computer simulations of the SiSB phase through the collapse/supernova phase in massive stars using state-of-the-art computational simulation codes to better understand this critical process for creating and dispersing atomic elements. The PI will present public lectures on supernova science and nucleosynthesis, or element creation, and train a graduate student in both stellar astrophysics and large-scale computation. The research team will simulate the developments in the last hour of convective silicon shell burning in a massive star and continue the simulations into the supernova explosion phase. The team will run a multi-dimensional code with realistic microphysics, including nucleosynthesis, neutrino transport, and turbulent convection. Since the code runs in three dimensions, they will be able to introduce asymmetries, which are known to be important, particularly for the supernova neutrino heating mechanism. The pre-collapse burning models will explore the limits of dimensionality, spatial resolution, nuclear network completeness, and duration required to adequately capture this dynamic stellar phase. The explosion simulations will calculate the element production from the supernova along with neutrino and gravitational wave signals. The proposed work will use a simulation code called Chimera, which the PI describes as a combination of three separate mature codes covering three aspects of the problem.