Constraining neutron-capture reactions for the astrophysical r process*

Neutron star mergers were recently found to be the only confirmed site for the astrophysical r process. This important discovery provided many answers regarding the possible r-process conditions and the synthesis of about half of the isotopes of the heavy elements in the Universe. However, it also created a large number of new questions and opportunities for nuclear physics. In my talk I will focus on some of the experimental aspects of these new opportunities. I will discuss the importance of neutron-capture reactions in the r process, and recent efforts to provide constraints using indirect techniques, in particular usinng the $\beta$-Oslo method. I will also discuss a new aspect of the r-process that was found in the recent GW170817 neutron-star merger observation, namely the kilonova afterglow of the event. I will present nuclear physics needs that can impact the interpretation of the observed electromagnetic spectra associated with the kilonova. The relevant experimental work discussed here was performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University using the $\gamma$-calorimeter SuN. Future plans for exciting new opportunities at FRIB will also be discussed.