Massive Stellar Evolution, Supernovae, and Nucleosynthesis

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Dr. Woosley will continue his extensive research on the origin of the elements and the end points of stellar evolution. This includes the evolution of massive stars (heavier than about 8 solar masses) through all stages of their lives, modeling their explosions and appearance as supernovae, calculating the detailed production of the isotopes of all the elements, and examining the properties of the neutron stars and black holes they leave behind. A major survey involving a large number of model stars will be completed and the results made available to the community. A limited range models will also be explored for rotating stars between 130 and 300 solar masses and for interacting binaries from 10 to 20 solar masses. Surveying a large number of stars is necessary to explore the sensitivity of the results to uncertain explosion parameters and to give the user a library from which to select various choices of explosion energy, stellar initial mass function, mass cut, rotation rate, and mixing. Stars in the lighter mass range may make common supernovae like the Crab, but have a novel explosion mechanism and contribute little to nucleosynthesis. Stars in the upper mass range encroach on the electron-positron pair instability after helium burning and may produce multiple, supernova-like outbursts that can be highly luminous. Multidimensional simulations of mixing and fall back and calculations of shock breakout, light curves and spectra will be carried out in a representative sample of all these models.Dr. Woosley's models are used as input by many other astrophysicists studying the evolution of galaxies, how supernovae explode, the nature of gamma-ray bursts, and the origin of neutron stars and black holes. They have previously circulated most of their models and results freely, even prior to publication, and will do so under this award. Their results and graphics are frequently used by the public media, recent examples being National Geographic Magazine, Sky and Telescope, Science News, and TV documentaries by Nova, the BBC and National Geographic. The work will also include graduate student training and international collaboration.