The link between rare earth peak formation and the astrophysical site of the $r$ process

Understand

The primary astrophysical source of the rare earth elements is the rapid neutron capture process ($r$ process).

• The rare earth peak that is seen in the solar $r$-process residuals has been proposed to originate as a pile-up of nuclei during the end of the $r$ process.
• We introduce a new method utilizing Monte Carlo studies of nuclear masses in the rare earth region, that includes self-consistently adjusting $\beta$-decay rates and neutron capture rates, to find the mass surfaces necessary for the formation of the rare earth peak.
• We demonstrate our method with two types of astrophysical scenarios, one corresponding conditions typical of core-collapse supernova winds and one corresponding to conditions typical of the ejection of the material from the tidal tails of neutron star mergers.