0 The First Hours of a Core Collapse Supernova

New two-dimensional, high-resolution calculations of a core collapse supernova in a 15 M ⊙ blue supergiant are presented, which cover the entire evolution from shock revival until the first few hours of the explosion. Explosive nucleosynthesis, its dependence upon convective mixing during the first second of the evolution and the growth of Rayleigh-Taylor instabilities at the composition interfaces of the progenitor star are all modeled consistently and allow for a comparison with observational data. We confirm our earlier findings, that the perturbations induced by neutrino driven convection are sufficiently strong to seed large-scale Rayleigh-Taylor mixing and to destroy the onion-shell structure of the stellar He-core. As in our earlier calculations, the strong deceleration of the nickel clumps in the layers adjacent to the He/H interface suggests that the high velocities of iron-group elements observed in SN 1987 A cannot be explained on the basis of currently favored progenitor models. Possible solutions to this dilemma and the implications of the mixing for type Ib explosions are briefly discussed. Recent observations of the Cas A remnant by NASA's Chandra X-ray observatory [3] appear to directly disclose for the first time the nature of the violent processes which are responsible for the synthesis of heavy and intermediate mass elements in core collapse supernovae. The spatial separation of silicon and iron emission observed by Hughes et al. [3] has been interpreted as the result of a large-scale overturn during the earliest phases of the explosion of the Cas A progenitor. Together with the numerous indications of strong mixing in e.g. SN 1987 A [1] and SN 1993 J [7] these new observations begin to assemble into a picture in which hydrodynamic instabilities in supernova explosions are inevitable and must be regarded as a key to an understanding of these events. Thus multidimensional hydrodynamic simulations are urgently required which must cover the entire evolution from shock formation until shock breakout through the stellar photosphere. In [5] we have reported on first preliminary results of such calculations and found that neutrino driven convection is able to seed strong Rayleigh-Taylor mixing at the Si/O and (C+O)/He interfaces of the SN 1987 A progenitor model of [8] within only about a minute after core bounce. The stellar metal core was found to have been completely shredded only five minutes after bounce and high-velocity clumps of newly synthesized elements were observed to be ejected up to the outer edge …