Shock Breakout in Core-collapse Supernovae and Its Neutrino Signature

We present results from dynamical models of core-collapse supernovae in one spatial dimension, employing a newly-developed Boltzmann neutrino radiation transport algorithm, coupled to Newtonian Lagrangean hydrodynamics and a consistent high-density nuclear equation of state. The transport method is multi-group, employs the Feautrier technique, uses the tangent-ray approach to resolve angles, is implicit in time, and is second-order accurate in space. We focus on shock breakout and follow the dynamical evolution of the cores of 11 M⊙, 15 M⊙, and 20 M⊙ progenitors through collapse and the first 250 milliseconds after bounce. The shock breakout burst is the signal event in core-collapse evolution, is the brightest phenomenon in astrophysics, and is largely responsible for the initial debilitation and stagnation of the bounce shock. As such, its detection and characterization could test fundamental aspects of the current collapse/supernova paradigm. We examine the effects on the emergent neutrino spectra, light curves, and mix of species (particularly in the early post-bounce epoch) of artificial opacity changes, the number of energy groups, the weak magnetism/recoil corrections, nucleon-nucleon bremsstrahlung, neutrino-electron scattering, and the compressibility of nuclear matter. Furthermore, we present the first highresolution look at the angular distribution of the neutrino radiation field both in the semi-transparent regime and at large radii and explore the accuracy with which our tangent-ray method tracks the free propagation of a pulse of radiation in a near vacuum. Finally, we fold the emergent neutrino spectra with the efficiencies and detection processes for a selection of modern underground neutrino observatories and argue that the prompt electron-neutrino breakout burst from the next galactic supernova is in principle observable and usefully diagnostic of fundamental collapse/supernova behavior. Though we are not in this study focusing on the supernova mechanism per se, our simulations support the theoretical conclusion (already reached by others) that spherical (1D) supernovae do not explode when good physics and transport methods are employed. Subject headings: supernovae, neutrinos, radiative transfer, spectra