Element abundance patterns in stars indicate fission of nuclei heavier than uranium
Ian U. Roederer, Nicole Vassh, Erika M. Holmbeck, Matthew R. Mumpower, Rebecca Surman, J. J. Cowan, Timothy C. Beers, Rana Ezzeddine, Anna Frebel, Terese T. Hansen, Vinicius M. Placco, Charli M. Sakari
Abstract
The heaviest chemical elements are naturally produced by the rapid neutron-capture process ( r -process) during neutron star mergers or supernovae. The r -process production of elements heavier than uranium (transuranic nuclei) is poorly understood and inaccessible to experiments so must be extrapolated by using nucleosynthesis models. We examined element abundances in a sample of stars that are enhanced in r -process elements. The abundances of elements ruthenium, rhodium, palladium, and silver (atomic numbers Z = 44 to 47; mass numbers A = 99 to 110) correlate with those of heavier elements (63 ≤ Z ≤ 78, A > 150). There is no correlation for neighboring elements (34 ≤ Z ≤ 42 and 48 ≤ Z ≤ 62). We interpret this as evidence that fission fragments of transuranic nuclei contribute to the abundances. Our results indicate that neutron-rich nuclei with mass numbers >260 are produced in r -process events.