ar X iv : a st ro - p h / 98 10 05 8 v 1 5 O ct 1 99 8 Core Collapse Supernovae — Theory between Achievements and New Challenges

Multi-dimensional hydrodynamic simulations of the post-bounce evolution of collapsed stellar iron cores have demonstrated that convective overturn between the stalled shock and the neutrinosphere can have an important effect on the neutrino-driven explosion mechanism. Whether a model yields a successful explosion or not, however, still depends on the power of neutrino energy deposition behind the stalled shock. The neutrino interaction with the stellar gas in the " hot bubble " also determines the duration of the shock stagnation phase, the explosion energy, and the composition of the neutrino-heated supernova ejecta. More accurate models require a more precise calculation of the neutrino luminosities and spectra and of the angular distributions of the neutrinos in the heating region. Therefore it is necessary to improve the numerical treatment of the neutrino transport, to develop a better understanding of the neutrino opacities of the dense nuclear medium, and to take into account convective processes inside the newly formed neutron star. 1 Convective instabilities — crucial for the explosion? 1.1 First hints from observations Supernova 1987A in the Large Magellanic Cloud, which was the nearest visible type II supernova for more than 380 years, brought a wealth of observational data. The neutrino measurements by the Kamiokande [24], IMB [6] and Baksan [1] laboratories confirmed expectations based on theoretical models that neutrinos play a crucial role during the collapse of the stellar core. The photon emission from the supernova revealed that large-scale deviations from spherical symmetry develop during the explosion. This was suggested by the fact that nickel clumps were seen moving at velocities much faster than predicted by spherically symmetric models for the layers where explosive nucleosynthesis of iron-group elements takes place. Very strong mixing of hydrogen deep into the stellar interior and of helium, metals and radioactive nuclei far out into the hydrogen envelope had to be invoked in order to reproduce the shape and the smoothness of the observed light curve [2, 50, 57] and to understand the early appearance of X-rays [17, 52] and γ-rays [36, 35, 15, 47] from SN 1987A. Efforts to explain the large extent of the mixing and the very high Ni velocities by hydrodynamic instabilities at the composition interfaces of the progenitor star failed [3, 16, 19, 21]. Therefore one was tempted to conclude that the anisotropies might originate from hydrodynamic instabilities during the very early moments of the explosion. 1.2 New dimensions in modeling This inspired …