GW170817 was really an event of the century that has opened the window to the frontier of multi-messenger astronomy and astrophysics. Gravitational waves from most likely the merging neutron stars were detected in LIGO-Virgo collaboration, GRB was observed in Fermi-GBM, and observed optical and near-infrared emissions in several Telescopes are consistent with those from radiative decays of r-process nuclei which are predicted theoretically in the nucleosynthesis calculation. Neutrinos were not detected unfortunately because of their too low flux from GW170817 that occurred at a distance 0.13 Gly away. We now await a nearby GW event (probably once per one-to-ten thousand years in our Milky Way) for spectroscopic observation of still unidentified r-process elements from neutron star mergers (NSMs).
In addition to the NSMs, core-collapse supernovae (of both magneto-hydrodynamic jet supernovae; MHD Jet-SNe, and neutrino-driven wind supernovae; nu-SNe) are viable candidates for the r-process sites. Supernova nucleosynthesis is expected to imprint significant evidence for the roles of neutrino interactions with matter including flavor oscillations. NSMs could not contribute to the early Galaxy for cosmologically long merging time-scale for slow GW radiation, while MHD Jet-SNe can explain the “universality” in the observed abundance pattern in metal poor stars. However, the NSM is still a possible nucleosynthetic site for the solar-system abundance. We would like to propose a novel solution to this twisted problem by carrying out both NSM and SN r-process nucleosynthesis calculations and numerical simulation of Galactic chemo-dynamical evolution. We will also discuss the impact of the SN nucleosynthesis on the physics of neutrino oscillations (including MSW, collective and vacuum oscillations).