Transuranic fission fragments in stars and prospects for multi-messenger astrophysics

I will summarize the evidence that fission fragments of transuranic elements have been detected among the abundance patterns of r-process-enhanced stars. A meta-analysis of 42 r-process-enhanced stars reveals that the elements Ru, Rh, Pd, and Ag (atomic numbers 44 ≤ Z ≤ 47, mass numbers 99 ≤ A ≤ 110) exhibit a correlation with abundances of heavier elements (63 ≤ Z ≤ 78, A > 150) that is not shared by their immediate neighbors (34 ≤ Z ≤ 42 and 48 ≤ Z ≤ 62). Coproduction via fission fragments of transuranic nuclei provides the most compelling explanation for this behavior. This signature provides the first evidence that neutron-rich fissioning nuclei with A > 260 are produced in r-process events. Finally, I will discuss prospects for detecting transuranic nuclei in multi-messenger observations of merging pairs of neutron stars and the kilonova events that accompany them.