Impact of Neutrino Interactions on Outflows of Neutron-Star Mergers

Abstract

Despite significant progress in the recent years a robust identification of the main astrophysical source or sources of the rapid-neutron-capture (r-) process is still lacking. Neutrino-driven winds in ordinary core-collapse supernovae seem to be ruled out as main r-process sources because of their insufficiently low neutron densities and entropies. Magnetorotationally driven supernovae might provide r-process conditions, but only if the magnetic field is strong enough (or builds up quickly enough) to launch the explosion on a sufficiently short timescale_s19 if or for how many progenitors this condition is met is largely unclear at the moment. Neutron-star (NS) mergers, i.e., mergers of two NSs or of a NS with a black hole (BH), could robustly produce r-process viable outflows in most events and by means of multiple ejecta components. Using a combination of neutrino-hydrodynamics simulations and post-processing nucleosynthesis calculations we investigated the different ejecta components and their r-process yields. Apart from the massive, nucleosynthesis relevant outflows also ultrarelativistic jets could emerge from the remnant of a NS merger. These jets are widely believed to explain the still mysterious origin of short gamma-ray bursts (sGRBs), but the main agent launching the jet remains disputed. We outline a recent study that explores one popular scenario in which the jet is being driven entirely due to heating by pair-annihilation of neutrinos.