R-process nucleosynthesis in the neutrino-heated relativistic collapsar jet model for gamma-ray bursts

We have investigated r-process nucleosynthesis within the collapsar jet model for long-duration gamma ray bursts. We simulated the core collapse of a rotating 35 solar mass progenitor star and followed the magnetohydrodynamic evolution to form a stable black-hole accretion disk. The transport of neutrinos emitted from the accretion disk was then evolved using a ray-tracing method to estimate the heating via neutrino pair annihilation in the polar region above the black hole leading to the production of a relativistic jet. We then distributed test particles in the outflow and followed the time evolution of the temperature, entropy, electron fraction, and density along each trajectory. Nuclear species were evolved for these trajectories with a large nuclear reaction network including more than 5,000 nuclei. We found that an r-process-like abundance distribution forms in material ejected in the collapsar jet.