Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. IV. Heavy Element Enhanced Stars
Abstract
We perform a homogeneous analysis of 82 heavy-element-enhanced metal-poor stars from the\\ LAMOST/Subaru sample, including 64 r-process-enhanced stars, 2 limited-r stars, and 16 stars exhibiting significant or moderate carbon enhancement (comprising 9 s-process-enhanced, 2 r-process-enhanced, 2 r/s, and 3 r+s stars). Systematic differences in [X/Eu] between r-I and r-II stars, together with their distinct dynamical properties, suggest that r-II stars likely formed in low-mass dwarf galaxies where contamination from additional nucleosynthetic channels was minimal. We have also discovered a number of peculiar objects. We identify an extremely metal-poor r-II star, J1158+0734 ([Fe/H] = -2.93), whose enhanced Zn abundance ([Zn/Fe] = +0.67) is best explained by yields from a high-energy, massive core-collapse supernova. The surface abundances of s-process-enhanced stars exhibit pronounced dispersion, consistent with enrichment from AGB progenitors with diverse properties. Notably, one star, J2256+0215, reveals compelling evidence for additional evolutionary mixing, as indicated by its unusually low carbon abundance ([C/Fe] = +0.08) and extremely low 12C/13C ratio of 2.33. Additionally, we identify 3 r+s stars whose abundance patterns reveal combined contributions from both the r- and s-processes. We further propose a modified diagnostic scheme for the identification of CEMP-r+s stars, defined as: -0.2 leqslant [La/Nd] leqslant 0.2 and -0.5 leqslant [Eu/Nd] leqslant 0.0.
Versions
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BibTeX
@misc{lin2026fourhundred,
title = {{Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. IV. Heavy Element Enhanced Stars}},
author = {Yangming Lin and Haining Li and Wako Aoki and Ruizheng Jiang and Tadafumi Matsuno and Zhenyu He and Ruizhi Zhang and Zhuohan Li and Satoshi Honda and Gang Zhao},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.40014},
eprint = {2610.40014},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.40014},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. IV. Heavy Element Enhanced Stars
AU - Yangming Lin
AU - Haining Li
AU - Wako Aoki
AU - Ruizheng Jiang
AU - Tadafumi Matsuno
AU - Zhenyu He
AU - Ruizhi Zhang
AU - Zhuohan Li
AU - Satoshi Honda
AU - Gang Zhao
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.40014
UR - https://arxiv.org/abs/2610.40014
AB - We perform a homogeneous analysis of 82 heavy-element-enhanced metal-poor stars from the\\ LAMOST/Subaru sample, including 64 r-process-enhanced stars, 2 limited-r stars, and 16 stars exhibiting significant or moderate carbon enhancement (comprising 9 s-process-enhanced, 2 r-process-enhanced, 2 r/s, and 3 r+s stars). Systematic differences in [X/Eu] between r-I and r-II stars, together with their distinct dynamical properties, suggest that r-II stars likely formed in low-mass dwarf galaxies where contamination from additional nucleosynthetic channels was minimal. We have also discovered a number of peculiar objects. We identify an extremely metal-poor r-II star, J1158+0734 ([Fe/H] = -2.93), whose enhanced Zn abundance ([Zn/Fe] = +0.67) is best explained by yields from a high-energy, massive core-collapse supernova. The surface abundances of s-process-enhanced stars exhibit pronounced dispersion, consistent with enrichment from AGB progenitors with diverse properties. Notably, one star, J2256+0215, reveals compelling evidence for additional evolutionary mixing, as indicated by its unusually low carbon abundance ([C/Fe] = +0.08) and extremely low ^12C/^13C ratio of 2.33. Additionally, we identify 3 r+s stars whose abundance patterns reveal combined contributions from both the r- and s-processes. We further propose a modified diagnostic scheme for the identification of CEMP-r+s stars, defined as: -0.2 leqslant [La/Nd] leqslant 0.2 and -0.5 leqslant [Eu/Nd] leqslant 0.0.
ER -