An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus
We report the discovery of an actinide-boost, very metal-poor ( $\left[{\rm{Fe}}/{\rm{H}}\right]=-2.38$ ), r -process-enhanced ( $\left[{\rm{Eu}}/{\rm{Fe}}\right]=0.80$ ) star, LAMOST J0804+5740, within the Gaia-Sausage-Enceladus (GSE). Based on the high-resolution ( R ∼ 36,000 and 60,000) and high...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/adc8a3 |
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| Summary: | We report the discovery of an actinide-boost, very metal-poor ( $\left[{\rm{Fe}}/{\rm{H}}\right]=-2.38$ ), r -process-enhanced ( $\left[{\rm{Eu}}/{\rm{Fe}}\right]=0.80$ ) 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 $\mathrm{log}\epsilon ({\rm{Th}}/{\rm{Eu}})=-0.22$ 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 $\hat{L}v$ = 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. |
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| ISSN: | 2041-8205 |