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The heaviest chemical elements are naturally produced by the rapid neutron-capture process (r-process) during neutron star mergers or supernovae. Ther-process production of elements heavier than uranium (transuranic nuclei) is poorly understood and inaccessible to experiments so must be extrapolated by using nucleosynthesis models. We examined element abundances in a sample of stars that are enhanced inr-process elements. The abundances of elements ruthenium, rhodium, palladium, and silver (atomic numbersZ= 44 to 47; mass numbersA= 99 to 110) correlate with those of heavier elements (63 ≤Z≤ 78,A> 150). There is no correlation for neighboring elements (34 ≤Z≤ 42 and 48 ≤Z≤ 62). We interpret this as evidence that fission fragments of transuranic nuclei contribute to the abundances. Our results indicate that neutron-rich nuclei with mass numbers >260 are produced inr-process events.
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Neutrino-driven Outflows and the Elemental Abundance Patterns of Very Metal-poor Stars
Abstract The elemental abundances between strontium and silver (Z= 38–47) observed in the atmospheres of very metal-poor stars in the Galaxy may contain the fingerprint of the weakr-process andνp-process occurring in early core-collapse supernovae explosions. In this work, we combine various astrophysical conditions based on a steady-state model to cover the richness of the supernova ejecta in terms of entropy, expansion timescale, and electron fraction. The calculated abundances based on different combinations of conditions are compared with stellar observations, with the aim of constraining supernova ejecta conditions. We find that some conditions of the neutrino-driven outflows consistently reproduce the observed abundances of our sample. In addition, from the successful combinations, the neutron-rich trajectories better reproduce the observed abundances of Sr–Zr (Z= 38–40), while the proton-rich ones, Mo–Pd (Z= 42–47).
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- PAR ID:
- 10522410
- Publisher / Repository:
- IOP
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 966
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 11
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/1538-4357/ad2dfb
