Nucleosynthesis Modes in the High-Entropy Wind of Type Ii Supernovae: Comparison of Calculations With Halo-Star Observations

While the high-entropy wind (HEW) of Type II supernovae remains one of the more promising sites for the rapid neutron-capture ( r -) process, hydrodynamic simulations have yet to reproduce the astrophysical conditions under which the latter occurs. We have performed large-scale network calculations within an extended parameter range of the HEW, seeking to identify or to constrain the necessary conditions for a full reproduction of all r -process residuals N r ,☉ = N ☉ − N s ,☉ by comparing the results with recent astronomical observations. A superposition of weighted entropy trajectories results in an excellent reproduction of the overall N r ,☉ pattern beyond Sn. For the lighter elements, from the Fe group via Sr–Y–Zr to Ag, our HEW calculations indicate a transition from the need for clearly different sources (conditions/sites) to a possible co-production with r -process elements, provided a range of entropies are contributing. This explains recent halo-star observations of a clear noncorrelation of Zn and Ge and a weak correlation of Sr–Zr with heavier r -process elements. Moreover, new observational data on Ru and Pd also seem to confirm a partial correlation with Sr as well as the main r -process elements (e.g., Eu).