Multi-messengers from the radioactive decay of $r$-process nuclei

Abstract

The radioactive ${\hat{I}}^2$-decay of nuclei synthesized in the rapid neutron capture process ($r$-process) releases a variety of particles, including electrons, ${\hat{I}}^3$-rays, neutrinos, and neutrons. These particles provide a rich set of multimessenger signals that carry information about the astrophysical environments where neutron-rich nucleosynthesis occurs. In this work, we calculate from first principles the emission spectra resulting from the ${\hat{I}}^2$-decay of $r$-process nuclei. Our approach incorporates detailed nuclear structure and decay data to model the energy distributions of each particle species. We couple the spectra with a nuclear reaction network simulation to obtain the temporal evolution of these distributions. We find that the emission distributions vary significantly in time and are non-thermal, with substantial average energies. We investigate these nuclear signals as a direct probe of heavy element formation and show that they are complementary observables to kilonova.

11 pages, 5 figures