Nucleosynthesis modes in the high-entropy-wind of type II supernovae

The exact conditions for the supernova high-entropy wind (HEW) as one of the favored sites for the rapid neutron-capture (r-) process still cannot be reproduced selfconsistently in present hydrodynamic simulations. Therefore, we have performed large-scale network calculations within a parameterized HEW model to constrain the necessary conditions for a full r-process, and to compare our results with recent astronomical observations. A superposition of entropy trajectories with model-inherent weightings results in an excellent reproduction of the overall solar-system isotopic abundances (Nr,⊙) of the “main” r-process elements beyond Sn. For the lighter r-elements, our model supports earlier qualitative ideas about a multiplicity of nucleosynthesis processes in the Fe-group region. In the high-entropy-wind scenario, these suggestions are quantified, and the origin of the “missing” abundances to Nr,⊙ is determined to be a rapid primary charged-particle (α-) process, thus excluding a classical “weak” neutron-capture component. This explains the recent halo-star observations of a non-correlation of Cu–Ge and Sr–Zr with metallicity [Fe/H] and r-process enrichment [Eu/H]. Moreover, for the first time a partial correlation with the “main” r-process is identified for Ru and Pd.