Nucleosynthesis Calculations Including the Astromer 85Kr

The nucleus ⁸⁵Kr 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 tied to the first excited state. We have computed the rate of transitions between these two ensembles, which is the internal equilibration rate for ⁸⁵Kr, and have also computed 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. With these results, we have included the two ensembles as two separate species (⁸⁵Kr_g and ⁸⁵Kr_m) in a nuclear reaction network and computed nucleosynthetic yields from a variety of astrophysical settings. We present the results of these calculations, with special attention paid to the role of the ⁸⁵Kr astromer.

We acknowledge support for this work under the Laboratory Directed Research and Development program of Los Alamos National Laboratory under Project Number(s) 20190021DR.