Abstract
It is quite likely that the site of the r process is the hot, neutron-rich “bubble” that expands off a protoneutron star during a core-collapse supernova. The process would then occur in an intense flux of neutrinos. In order to explore the consequences of the neutrino irradiation, we calculate the rates of charged-current and neutral-current neutrino reactions on neutron-rich heavy nuclei, and estimate the average number of neutrons emitted in the resulting spallation. Our results suggest, for a dynamic process occurring in an expanding bubble, that charged-current captures might help shorten the time scale for the process, bringing it into better accord with our expectations about the conditions in the hot bubble: neutrino reactions can be important in breaking through the waiting-point nuclei at and 82, while still allowing the formation of abundance peaks. Furthermore, after the process freezes out, there appear to be distinctive neutral-current and charged-current postprocessing effects. These include a spreading of the abundance peaks and damping of the most pronounced features (e.g., peaks and valleys) in the unpostprocessed abundance distribution. Most importantly, a subtraction of the neutrino postprocessing effects from the observed solar -process abundance distribution shows that two mass regions, –126 and 183–187, are inordinately sensitive to neutrino postprocessing effects. This imposes very stringent bounds on the freeze-out radii and dynamic time scales governing the process. Moreover, we find that the abundance patterns within these mass windows are entirely consistent with synthesis by neutrino interactions. This strongly argues that the process must occur in the intense neutrino flux provided by a core-collapse supernova. It also greatly restricts dynamic models for the supernova -process nucleosynthesis.
- Received 5 November 1996
DOI:https://doi.org/10.1103/PhysRevC.55.1532
©1997 American Physical Society