Co-production of light p-, s- and r-process isotopes in the high-entropy wind of type II supernovae

The nucleosynthesis origin of the light trans-Fe elements in the Solar System (SS), historically believed to be composed of different fractions of the p-, s- and r-processes, has been a fascinating subject for nuclear astrophysicists since more than 50 years. However, even the most recent astrophysical models have major short-comings the one or other way. We have performed large-scale dynamical network calculations within the high-entropy wind (HEW) scenario of SNe II in order to constrain the astrophysical conditions for the nucleosynthesis of the light trans-Fe elements. We find that for electron fractions in the range 0.450 ≤Ye≤0.495, only minor amounts of Zn to Rb but high abundances of the classical p-, s- and r-process nuclei of Sr to Ru are co-produced at low entropies (S) after an α-rich freeze out. No initial abundances of p-, s- or r-process seeds need to be invoked; hence, all components are primary, rather than secondary. Taking the isotopic composition of Mo as a particularly interesting example, we show that HEW trajectories with Ye≅0.46 and S≤50 are able to reproduce the SS ratio of 92Mo/94Mo. Furthermore, for slightly higher Ye and S trajectories, our nucleosynthesis results can also explain the anomalous abundances of the Mo isotopes recently measured in SiC grains of type X, which are likely SN condensates.