The r-process in supernova explosions from the collapse of ONeMg cores

We examine r-process nucleosynthesis in a "prompt supernova explosion" from an 8 - 10M circle dot progenitor star. In the present model, the progenitor star has formed an oxygen-neon-magnesium core at its center. The core-collapse simulations are performed with a one-dimension, Newtonian hydrodynamic code. We simulate energetic prompt explosions by enhancement of the shock-heating energy, in order to investigate conditions necessary for the production of r-process nuclei in such events. The r-process nucleosynthesis is calculated using a nuclear reaction network code including relevant neutron-rich isotopes with reactions among them. The highly neutronized ejecta (Y approximate to 0.14 - 0.20) leads to robust production of r-process nuclei; their relative abundances are in excellent agreement with the solar r-process pattern. Our results suggest that prompt explosions of 8 - 10M circle dot stars with oxygen-neon-magnesium cores can be a promising site of r-process nuclei.