Hans A. Bethe Prize: Astrophysical, observational and nuclear-physics aspects of r-process nucleosynthesis

Guided by the Solar System (S.S.) abundance peaks at A$\simeq$130 and A$\simeq$195, the basic mechanisms for the rapid neutron-capture process (the {\it r-process}) have been known for over 50 years. However, even today, all proposed scenarios and sites face problems with astrophysical conditions as well as with the necessary nuclear-physics input. In my talk, I will describe efforts in experimental and theoretical nuclear-structure data for modeling today's three groups of r-process {\it ``observables''}, i.e. the bulk S.S. isotopic abundances, the elemental abundances in metal-poor halo stars, and peculiar isotopic patterns measured in certain cosmic stardust grains. To set a historical basis, I will briefly recall our site-independent {\it ``waiting-point''} model, with superpositions of neutron-density components and the use of the first global, unified nuclear input based on the mass model FRDM(1992). This approach provided a considerable leap forward in the basic understanding of the required astrophysical conditions, as well as of specific shell-structure properties far from stability. Starting in the early millenium, the above simple model has been replaced by more realistic, dynamical parameter studies within the high-entropy wind scenario of core-collapse supernovae, now with superpositions of entropy (S) and electron-fraction (Y$_e$) components. Furthermore, an improved, global set of nuclear-physics data is used today, based on the new mass model FRDM(2012). With this nuclear and astrophysics parameter combination, a new fit to the S.S. r-abundances will be shown, and its improvements and remaining deficiencies in terms of underlying shell structure will be discussed. Concerning the abundance patterns in metal-poor halo stars, an interpretation of the production of {\it ``r-rich''} (e.g. CS 22892-052) and {\it ``r-poor''} (e.g. HD 122563) stars in terms of different (Y$_e$), S combinations will be presented. Finally, for the third group of {\it ``r-observables''}, a possible origin of the anomalous Xe-H pattern in presolar nanodiamonds by the {\it ``main''} component of a {\it ``cold''} r-process is suggested.