ASCERTAINING THE CORE COLLAPSE SUPERNOVA MECHANISM: The State of the Art and the Road Ahead

Abstract

▪ Abstract  More than four decades have elapsed since modeling of the core collapse supernova mechanism began in earnest. To date, the mechanism remains elusive, at least in detail, although significant progress has been made in understanding these multiscale, multiphysics events. One-, two-, and three-dimensional simulations of or relevant to core collapse supernovae have shown that (a) neutrino transport, (b) fluid instabilities, (c) rotation, and (d) magnetic fields, together with proper treatments of (e) the sub- and super- nuclear density stellar core equation of state, (f) the neutrino interactions, and (g) gravity are all important. The importance of these ingredients applies to both the explosion mechanism and to phenomena directly associated with the mechanism, such as neutron star kicks, supernova neutrino and gravitational wave emission, and supernova spectropolarimetry. Not surprisingly, current two- and three-dimensional models have yet to include (a)–(d) with sufficient realism. One-dimensional spherically symmetric models have achieved a significant level of sophistication but, by definition, cannot incorporate (b)–(d), except phenomenologically. Fully general relativistic spherically symmetric simulations with Boltzmann neutrino transport do not yield explosions, demonstrating that some combination of (b), (c), and (d) is required to achieve this. Systematic layering of the dimensionality and the physics will be needed to achieve a complete understanding of the supernova mechanism and phenomenology. The past modeling efforts alluded to above have illuminated that core collapse supernovae may be neutrino driven, magnetohydrodynamically (MHD) driven, or both, but uncertainties in the current models prevent us from being able to answer even this most basic question. And it may be that more than one possibility is realized in nature. Nonetheless, if a supernova is neutrino driven, magnetic fields will likely have an impact on the dynamics of the explosion. Similarly, if a supernova is MHD driven, the neutrino transport will dictate the dynamics of stellar core collapse, bounce, and the postbounce evolution, which in turn will create the environment in which an MHD-driven explosion would occur. Thus, although reduction will allow us to sort out the roles of each of the major physics components listed above, we will not obtain a quantitative, and perhaps even qualitative, understanding of core collapse supernovae until all components and their coupling are included in the models with sufficient realism.