Differentiating Electron-Capture and Core-Collapse Supernovae

Core-collapse supernovae mark the deaths of massive stars and the formation of neutron stars and black holes. Beyond the visual display from which they draw their name, they are also marked by the release of tremendous fluxes of neutrinos and the ejection into their galaxy of prodigious quantities of newly made atomic nuclei. In fact, it is the neutrino flux which powers the explosion. Much of the chemical composition of our planet and ourselves comes originally from these explosions, thus core-collapse supernovae are an essential link in our chain of origins. With this project, state-of-the-art simulations of the formation of the neutron star, the emission of the neutrinos and the formation of new atomic nuclei will be extended to the epoch, hours to days later, when these newly made elements become visible to telescopic observations. In parallel, state-of-the-art models of supernovae will be extended to less common, less well studied, electron-capture supernovae, which occur in somewhat less massive, super Asymptotic Giant Branch stars. In the process, two graduate students will be trained in both nuclear astrophysics and computational science, equipping them to join the STEM workforce upon graduation.This project will result in a world-leading ability to simulate core-collapse and electron-capture supernovae, calculate their nucleosynthesis, and compare these predictions with observations of supernovae, supernova remnants and galactic chemical evolution. The inclusion in the CHIMERA code of arbitrary nuclear reaction networks is a significant advantage for these studies. For electron-capture supernovae, inclusion of a couple hundred nuclear species is underway, allowing for much more complete coverage of the electron captures that initiate the explosion than has previously been possible. Inclusion of 160 nuclear species has already been demonstrated in CHIMERA for core-collapse supernovae, providing the most extensive representation of the nuclear composition in a multi-dimensional model of a core collapse supernova to date. Extension of both core-collapse and electron capture simulations, with their detailed representation of the nuclear composition, through the entire stellar envelope and into the circumstellar medium until the ejecta achieves homology, opens the possibility to constrain these models with photonic observations from days to months after explosion, as the composition and distribution of the elements plays an essential role in these observations. Thus these models will shed light on the shortcomings in our current understanding of supernova nucleosynthesis.This project advances the objectives of "Windows on the Universe: the Era of Multi-Messenger Astrophysics", one of the 10 Big Ideas for Future NSF Investments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.