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Recent observational advances have enabled high resolution mapping of 44Ti in core-collapse supernova (CCSN) remnants. Comparisons between observations and models provide stringent constraints on the CCSN mechanism. However, past work has identified several uncertain nuclear reaction rates that influence 44Ti and 56Ni production in postprocessing model calculations. We evolved one-dimensional models of 15 M ⊙, 18 M ⊙, 22 M ⊙, and 25 M ⊙ stars from zero age main sequence through CCSN using Modules for Experiments in Stellar Astrophysics and investigated the previously identified reaction rate sensitivities of 44Ti and 56Ni production. We tested the robustness of our results by making various assumptions about the CCSN explosion energy and mass cut. We found a number of reactions that have a significant impact on the nucleosynthesis of 44Ti and 56Ni, particularly for lower progenitor masses. Notably, the reaction rates , , , , , , , , , , and are influential for a large number of model conditions. Furthermore, we found the list of influential reactions identified by previous postprocessing studies of CCSN shock-driven nucleosynthesis is likely incomplete, motivating future larger-scale sensitivity studies.

We find that the proton separation energy, S(p), of 73 Rb is −640(40) keV, deduced from the observation of β-delayed ground-state protons following the decay of 73 Sr. This lower-limit determination of the proton separation energy of 73 Rb coupled with previous upper limits from nonobservation, provides a full constraint on the mass excess with M( 73 Rb) =−46.01 ± 0.04 MeV. With this new mass excess and the excitation energy of the J π = 5/2 − isobaric-analog state (T = 3/2) in 73 Rb, an improved constraint can be put on the mass excess of 73 Sr using the isobaric-multiplet mass equation (IMME), and we find M( 73 Sr) =−31.98 ± 0.37 MeV. These new data were then used to study the composition of ashes on accreting neutron stars following Type I xray bursts. Counterintuitively, we find that there should be an enhanced fraction of A > 102 nuclei with more negative proton separation energies at the 72 Kr rp-process waiting point. Larger impurities of heavier nuclei in the ashes of accreting neutron stars will impact the cooling models for such astrophysical scenarios.

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