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G. C. Jordan IV, B. S. Meyer (Clemson University)
The yield of 57Ni in core-collapse supernovae as determined by observations of gamma rays from the decay of daughter 57Co gives important constraints on supernova models. In the alpha-rich freezeout resulting from core-collapse supernovae, 56Co (produced as parent 56Ni) and 57Co (produced as parent 57Ni) are identified as important observables. In the present work, we have surveyed the cross-section sensitivities of the nucleosythesis of 56Ni and 57Ni, by systematically varying reaction cross-sections and groups of reaction cross-sections to identify the most important reaction(s) for the production of 56Ni and 57Ni. The alpha-rich freezeout yield of 56Ni is extremely robust against factors of ten changes in any strong or electromagnetic cross-section. This is expected since this nucleus is largely produced in equilibrium. 57Ni is also extremely robust against changes in all reaction cross-sections except for the reaction 57Ni(n,p)57Co. This reaction determines when 57Ni breaks out of quasi-equilibrium. The magnitude of the effect is such that an increase (decrease) by a factor of three in the reaction cross-section from the standard value leads to about a 10 percent decrease (increase) in the 57Ni yield. Hence, an accurate measurement of this reaction (or the reverse) cross-section would improve the predictions of the models, thereby leading to better constraints on them.