Dynamics of shock propagation and nucleosynthesis conditions in O-Ne-Mg core supernovae

Abstract

It has been recently proposed that the shocked surface layer s of exploding O-Ne-Mg cores provide the conditions for r-process nucleosynthesis, because their rapid expansion and high entropies enable heavy r-process isotopes to form even in an environment with very low initial neutron excess of the matter. We show here that the most sophisticated available hydrodynamic simulations (in spherical and axial symmetry) do not support this new r-process scenario because they fail to provide the necessary conditions of temperature, entropy, and expansion timescale by significa nt factors. This suggests that, either the formation of r-pr ocess elements works differently than suggested by Ning et al. (2007, NQM07), or that some essential core properties with influence on the explosio n dynamics might be different from those predicted by Nomoto’s progenitor model.