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

TL;DR

This paper critically examines the proposed r-process nucleosynthesis in O-Ne-Mg core supernovae, finding that current hydrodynamic simulations do not support the necessary conditions for this process, challenging previous hypotheses.

Contribution

It provides a detailed analysis showing that existing simulations do not meet the conditions for r-process nucleosynthesis in O-Ne-Mg supernovae, questioning earlier theoretical proposals.

Findings

Simulations fail to produce required temperature and entropy conditions.

Expansion timescales in simulations are insufficient for r-process.

The proposed r-process scenario may need revision or alternative explanations.

Abstract

It has been recently proposed that the shocked surface layers 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 significant factors. This suggests that, either the formation of r-process elements works differently than suggested by Ning et al. (2007, NQM07), or that some essential core properties with influence on the explosion dynamics might be different from those predicted by Nomoto's progenitor model.