Nucleosynthesis s-Process Calculations Including the Astromer ⁸⁵Kr

The ⁸⁵Kr nucleus is an astrophysical isomer (an "astromer") since its excited states can be out of equilibrium with its ground state in astrophysical environments. We have computed the nuclear properties of ⁸⁵Kr as two separate ensembles of states: one tied to the ground state and one to the excited state. We have computed the rate of transitions between these two ensembles, which is the internal equilibration rate for ⁸⁵Kr, and the transition rates between other species and these two ensembles, such as neutron capture into the ensembles from ⁸⁴Kr and neutron capture out of each ensemble to ⁸⁶Kr. We have included these rates in a nuclear reaction network and computed nucleosynthetic yields from a set of parameterized s-process trajectories. We delineate four regimes of s-process branching at ⁸⁵Kr depending on the competition among neutron-capture, beta-decay, and isomerization rates and show how s-process ows vary as the system evolves through these dierent regimes. We also confirm our treatment of isomerization with a full equilibration model for ⁸⁵Kr and have developed open-source codes that allow users to treat other astromers with our methods.