Four-hundred very metal-poor stars studied with LAMOST and Subaru: IV. Heavy element enhanced stars
We perform a homogeneous analysis of 82 heavy-element-enhanced metal-poor stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) /Subaru sample, including 64 r-process-enhanced stars, two limited-r stars, and 16 stars exhibiting significant or moderate carbon enhancement (...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
2026 May 15
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| In: |
The astrophysical journal
Year: 2026, Volume: 1003, Issue: 1, Pages: 1-26 |
| ISSN: | 1538-4357 |
| DOI: | 10.3847/1538-4357/ae5a3d |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.3847/1538-4357/ae5a3d
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| Author Notes: | Yangming Lin, Haining Li, Wako Aoki, Ruizheng Jiang, Tadafumi Matsuno, Zhenyu He, Ruizhi Zhang, Zhuohan Li, Satoshi Honda, and Gang Zhao |
| Summary: | We perform a homogeneous analysis of 82 heavy-element-enhanced metal-poor stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) /Subaru sample, including 64 r-process-enhanced stars, two limited-r stars, and 16 stars exhibiting significant or moderate carbon enhancement (comprising nine s-process-enhanced, two r-process-enhanced, two r/s, and three 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 asymptotic giant branch (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 three carbon-enhanced metal-poor (CEMP) 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 ≤ [La/Nd] ≤ 0.2 and −0.5 ≤ [Eu/Nd] ≤ 0.0. |
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| Item Description: | Gesehen am 10.07.2026 |
| Physical Description: | Online Resource |
| ISSN: | 1538-4357 |
| DOI: | 10.3847/1538-4357/ae5a3d |