Hydrodynamical Study of Neutrino-Driven Wind as an r-Process Site

We study the neutrino-driven wind from the proto-neutron star by the generalrelativistic hydrodynamical simulations. We examine the properties of theneutrino-driven wind to explore the possibility of the r-processnucleosynthesis. The numerical simulations with the neutrino heating andcooling processes are performed with the assumption of the constant neutrinoluminosity by using realistic profiles of the proto-neutron star (PNS) as wellas simplified models. The dependence on the mass of PNS and the neutrinoluminosity is studied systematically. Comparisons with the analytic treatmentin the previous studies are also done. In the cases with the realistic PNS, wefound that the entropy per baryon and the expansion time scale are neither highnor short enough for the r-process within the current assumptions. On the otherhand, we found that the expansion time scale obtained by the hydrodynamicalsimulations is systematically shorter than that in the analytic solutions dueto our proper treatment of the equation of state. This fact might lead to theincrease of the neutron-to-seed ratio, which is suitable for the r-process inthe neutrino-driven wind. Indeed, in the case of massive and compactproto-neutron stars with high neutrino luminosities, the expansion time scaleis found short enough in the hydrodynamical simulations and the r-processelements up to A ~ 200 are produced in the r-process network calculation.Comment: 24 pages, 9 figures. Submitted to PAS