Year: 2025
Type: article
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.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,400
Funders: European Space Agency, National Natural Science Foundation of China, Chinese Academy of Sciences, National Astronomical Observatory of Japan, National Development and Reform Commission, Japan Society for the Promotion of Science, National Astronomical Observatories, Chinese Academy of Sciences
OpenAlex ID: W4410123867