Ab initio nuclear mass predictions at N=126 and the third r-process abundance peak

Studies of the astrophysical rapid neutron capture process (r-process) have used the Solar abundances as a benchmark for decades. Discrepancies between the Solar pattern and nucleosynthesis predictions can provide hints as to whether a given set of nuclear physics assumptions or a given astrophysical site is in tension with being labeled as a key source of Solar System enrichment. In particular, the third r-process peak at mass number A=195 can be directly connected to the properties of the N=126 shell closure which are currently largely unprobed by experiment. In this talk I will present masses calculated with IMSRG ab initio nuclear theory at N=126 for the first time. We then propagate these masses to the nuclear data needed for the nucleosynthesis calculation and show the impact of these new masses on predictions for the abundances of the third peak. Many exciting new measurements at N=126 are coming in the near future, however as they are not projected to reach all the way to the dripline, theory developments in this regime are incredibly important to understand the production of noteworthy r-process species such as gold and platinum, as well as the r-process reach into the actinides.