Constraining Nucleosynthesis in Neutrino-driven Winds: Observations, Simulations, and Nuclear Physics

A promising astrophysical site to produce the lighter heavy elements of the first r-process peak (Z = 38 - 47) is the moderately neutron-rich (0.4 < Y ( e ) < 0.5) neutrino-driven ejecta of explosive environments, such as core-collapse supernovae and neutron star mergers, where the weak r-process operates. This nucleosynthesis exhibits uncertainties from the absence of experimental data from (alpha, xn) reactions on neutron-rich nuclei, which are currently based on statistical model estimates. In this work, we report on a new study of the nuclear reaction impact using a Monte Carlo approach and improved (alpha, xn) rates based on the Atomki-V2 alpha optical model potential. We compare our results with observations from an up-to-date list of metal-poor stars with [Fe/H] < -1.5 to find conditions of the neutrino-driven wind where the lighter heavy elements can be synthesized. We identified a list of (alpha, xn) reaction rates that affect key elemental ratios in different astrophysical conditions. Our study aims to motivate more nuclear physics experiments on (alpha, xn) reactions using the current and new generation of radioactive beam facilities and also more observational studies of metal-poor stars.