The r-process in neutrino-driven winds from nascent, "compact" neutron stars of core-collapse supernovae

We present calculations of r-process nucleosynthesis in neutrino-driven win ds from the nascent neutron stars of core-collapse supernovae. A full dynam ical reaction network for both the alpha -rich freezeout and the subsequent r-process is employed. The physical properties of the neutrino-heated ejec ta are deduced from a general relativistic model in which spherical symmetr y and steady flow are assumed. Our results suggest that proto-neutron stars with a large compaction ratio provide the most robust physical conditions for the r-process. The third peak of the r-process is well reproduced in th e winds from these "compact" proto-neutron stars even for a moderate entrop y, similar to 100N (A)k-200N (A)k, and a neutrino luminosity as high as sim ilar to 10(52) ergs s(-1). This is due to the short dynamical timescale of material in the wind. As a result, the overproduction of nuclei with A less than or similar to 120 is diminished (although some overproduction of nucl ei with A approximate to 90 is still evident). The abundances of the r-proc ess elements per event is significantly higher than in previous studies. Th e total integrated nucleosynthesis yields are in good agreement with the so lar r-process abundance pattern. Our results have confirmed that the neutri no-driven wind scenario is still a promising site in which to form the sola r r-process abundances. However, our best results seem to imply both a rath er soft neutron-star equation of state and a massive protoneutron star that is difficult to achieve with standard core-collapse models. We propose tha t the most favorable conditions perhaps require that a massive supernova pr ogenitor forms a massive protoneutron star by accretion after a failed init ial neutrino burst.