The r-process in supersonic neutrino-driven winds: The roll of wind termination shock

Recent hydrodynamic studies of core-collapse supernovae imply that the neutrino-heated ejecta from a nascent neutron star develops to supersonic outflows and forms the wind termination shock. We investigate the effects of the termination shock in neutrino-driven winds and its role on the r-process. We find a couple of effects that can be relevant for the r-process. First is the sudden slowdown of the temperature decrease by the wind termination plays a decisive role to determine the r-process abundance curves. This is due to the strong dependences of the nucleosynthetic path on the temperature during the r-process freezeout phase. Second is the entropy jump by termination-shock heating, up to several 100N(A)k. We, however, find negligible roles of the entropy jump on the r-process. This is a consequence that the sizable entropy increase takes place only at a large shock radius (greater than or similar to 10,000 km) where the r-process has already ceased.