Please contact divya.singh@berkeley.edu, tianqi.zhao@berkeley.edu, or klund@berkeley.edu for zoom links.

The rapid neutron-capture (r-) process is responsible for producing approximately half of the elements heavier than iron in the Universe. However, the astrophysical sites capable of generating the required extreme neutron fluxes remain uncertain. Detailed hydrodynamical simulations of proposed scenarios – such as binary neutron star mergers, magneto-rotational supernovae, and collapsars – are computationally demanding and subject to significant uncertainties, including the nuclear equation of state, neutrino interactions, and progenitor properties.

To address these challenges, we adopt a site-independent approach, based on a parametric density profile. Using nuclear network calculations, we explore a broad range of initial electron fractions, entropies, and expansion timescales. Our results reproduce those obtained in hydrodynamical simulations and extend beyond currently explored conditions. We find that two to three distinct ejecta components are required to reproduce the typical r-process abundance pattern.

In addition to astrophysical uncertainties, poorly constrained nuclear properties introduce significant theoretical uncertainties. Most nuclei along the r-process path are experimentally inaccessible, making reliable theoretical predictions of nuclear masses, reaction rates, and fission properties essential. We investigate the impact of ab initio nuclear mass predictions around the N=82 shell closure (associated with the second r-process peak), calculated using the Valence-Space In-Medium Similarity Renormalization Group (VS-IMSRG) method.