Searching for Signatures of i-process Nucleosynthesis in Metal-Rich, Lead-rich Barium Stars

@misc{manea2026searching,
  title = {{Searching for Signatures of i-process Nucleosynthesis in Metal-Rich, Lead-rich Barium Stars}},
  author = {Catherine Manea and Madeleine McKenzie and Gail Zasowski and Giulia C. Cinquegrana and Amaya Sinha and Sarah G. Kane and Jaden Levine and Ellie Mebius and Aleksandra Winkler},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.05470},
  eprint = {2611.05470},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.05470},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Searching for Signatures of i-process Nucleosynthesis in Metal-Rich, Lead-rich Barium Stars
AU  - Catherine Manea
AU  - Madeleine McKenzie
AU  - Gail Zasowski
AU  - Giulia C. Cinquegrana
AU  - Amaya Sinha
AU  - Sarah G. Kane
AU  - Jaden Levine
AU  - Ellie Mebius
AU  - Aleksandra Winkler
PY  - 2026
DA  - 2026/11/03
PB  - arXiv
DO  - 10.48550/arxiv.2611.05470
UR  - https://arxiv.org/abs/2611.05470
AB  - The intermediate neutron-capture process (i-process) has been invoked to explain the peculiar compositions of carbon-enhanced metal-poor (CEMP) stars enriched in both slow- (s) and rapid- (r) neutron-capture elements. Recent literature has questioned its operation at higher metallicities, but observational evidence remains limited. We analyse Gemini/GHOST and McDonald/Tull spectra of six -0.7 < [Fe/H] < −0.1 stars identified in GALAH by their extreme Ba and Eu (or Sm) compositions (≳10× solar). We also reanalyse archival spectra of two literature i-process candidates. We determine abundances in up to 42 elements (Li through Pb), ^12C/^13C, and Mg isotopic ratios, and compare to literature barium and CEMP stars and multiple asymptotic giant branch (AGB) model grids. Three stars exhibit extreme [Pb/Fe] (+1.79±0.19 to +2.50±0.32 dex), and two extreme [Eu/Fe] (+1.10±0.11 to +1.30±0.11 dex), distinguishing them from typical metal-rich barium stars. Two of these three exhibit abundance patterns that are inconsistent with s-process models and best explained by existing i-process predictions. The remaining sample is either consistent with s-process enrichment or suggestive of atomic diffusion. Both literature candidates are well-fit by the i-process model, but conventional s-process enrichment cannot be excluded. Our findings reinforce that metal-rich AGB stars contribute to the production of elements classically attributed to the r-process. These results identify promising candidates for i-process enrichment near solar metallicity and motivate additional i-process models to understand the contribution of this nucleosynthetic process to the chemical evolution of the Milky Way disk.
ER  -