科研之友
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摘要
We use results from long-time core-collapse supernovae simulations to investigate the impact of the late time evolution of the ejecta and of the nuclear physics input on the calculated r-process abundances. Based on the latest hydrodynamical simulations, heavy r-process elements cannot be synthesized in the neutrino-driven winds that follow the supernova explosion. However, by artificially increasing the wind entropy, elements up to A = 195 can be made. In this way one can reproduce the typical behavior of high-entropy ejecta where the r process is expected to occur. We identify which nuclear physics input is more important depending on the dynamical evolution of the ejecta. When the evolution proceeds at high temperatures (hot r process), an (n, gamma)reversible arrow(gamma, n) equilibrium is reached, while at low temperatures (cold r process) there is a competition between neutron captures and beta decays. In the first phase of the r process, while enough neutrons are available, the most relevant nuclear physics inputs are the nuclear masses for the hot r process and the neutron capture and beta-decay rates for the cold r process. At the end of this phase, the abundances follow a steady beta flow for the hot r process and a steady flow of neutron captures and beta decays for the cold r process. After neutrons are almost exhausted, matter decays to stability and our results show that in both cases neutron captures are key for determining the final abundances, the position of the r-process peaks, and the formation of the rare-earth peak. In all the cases studied, we find that the freeze-out occurs in a time scale of several seconds.
- 出版日期2011-4-27
