An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus

作者：Yangming Lin, Haining Li, Ruizheng Jiang, Wako Aoki, Satoshi Honda, Zhenyu He, Ruizhi Zhang, Zhuohan Li, Gang Zhao · 发表于：The Astrophysical Journal Letters · 年份：2025 · DOI：10.3847/2041-8213/adc8a3 · 被引用次数：5 · 研究领域：Stellar, planetary, and galactic studies、Astro and Planetary Science、Gamma-ray bursts and supernovae

Abstract We report the discovery of an actinide-boost, very metal-poor ( Fe / H = − 2.38 ), r -process-enhanced ( Eu / Fe = 0.80 ) star, LAMOST J0804+5740, within the Gaia-Sausage-Enceladus (GSE). Based on the high-resolution ( R ∼ 36,000 and 60,000) and high signal-to-noise ratio spectra obtained with the High Dispersion Spectrograph on the Subaru Telescope, the abundances of 48 species are determined. Its log ϵ ( Th / Eu ) = − 0.22 establishes it as the first confirmed actinide-boost star within the GSE. Comparative analysis of its abundance pattern with theoretical r -process models reveals that the magnetorotationally driven jet supernova r -process model with L ˆ v = 0.2 provides the best fit and successfully reproduces the actinide-boost signature. Kinematic analysis of actinide-boost stars reveals that approximately two-thirds of them are classified as ex situ stars, suggesting that actinide-boost stars are more likely to originate from accreted dwarf galaxies. As the first actinide-boost star identified within the GSE, J0804+5740 will provide valuable insights into r -process nucleosynthesis in accreted dwarf galaxies like the GSE, especially on the production of the heaviest elements.