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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2025-01-01
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| Series: | The Astrophysical Journal Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/adc8a3 |
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| author | Yangming Lin Haining Li Ruizheng Jiang Wako Aoki Satoshi Honda Zhenyu He Ruizhi Zhang Zhuohan Li Gang Zhao |
| author_facet | Yangming Lin Haining Li Ruizheng Jiang Wako Aoki Satoshi Honda Zhenyu He Ruizhi Zhang Zhuohan Li Gang Zhao |
| author_sort | Yangming Lin |
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| description | 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 |
| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal Letters |
| spelling | doaj-art-de9c6268892a460daacc81be355aabfc2025-08-20T02:11:30ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019842L4310.3847/2041-8213/adc8a3An Actinide-boost Star Discovered in the Gaia-Sausage-EnceladusYangming Lin0https://orcid.org/0009-0000-8769-3142Haining Li1https://orcid.org/0000-0002-0389-9264Ruizheng Jiang2https://orcid.org/0009-0001-0604-072XWako Aoki3https://orcid.org/0000-0002-8975-6829Satoshi Honda4https://orcid.org/0000-0001-6653-8741Zhenyu He5https://orcid.org/0009-0002-0124-9492Ruizhi Zhang6https://orcid.org/0009-0008-1319-1084Zhuohan Li7https://orcid.org/0000-0002-1126-9289Gang Zhao8https://orcid.org/0000-0002-8980-945XCAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Chinese Academy of Sciences, Beijing 100101, People’s Republic of China ; lhn@nao.cas.cn; School of Astronomy and Space Science, University of Chinese Academy of Sciences , No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of ChinaCAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Chinese Academy of Sciences, Beijing 100101, People’s Republic of China ; lhn@nao.cas.cnCAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Chinese Academy of Sciences, Beijing 100101, People’s Republic of China ; lhn@nao.cas.cn; School of Astronomy and Space Science, University of Chinese Academy of Sciences , No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of ChinaNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Astronomical Science Program, The Graduate University for Advanced Studies , SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanNishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo , 407-2, Nishigaichi, Sayo-cho, Sayo, Hyogo 679-5313, JapanSchool of Physics, Peng Huanwu Collaborative Center for Research and Education, and International Research Center for Big-Bang Cosmology and Element Genesis, Beihang University , Beijing 100191, People’s Republic of China; ShenYuan Honors College, Beihang University , Beijing 100191, People’s Republic of ChinaCAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Chinese Academy of Sciences, Beijing 100101, People’s Republic of China ; lhn@nao.cas.cnCAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Chinese Academy of Sciences, Beijing 100101, People’s Republic of China ; lhn@nao.cas.cn; School of Astronomy and Space Science, University of Chinese Academy of Sciences , No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of ChinaCAS Key Laboratory of Optical Astronomy, National Astronomical Observatories , Chinese Academy of Sciences, Beijing 100101, People’s Republic of China ; lhn@nao.cas.cn; School of Astronomy and Space Science, University of Chinese Academy of Sciences , No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of ChinaWe 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.https://doi.org/10.3847/2041-8213/adc8a3Chemically peculiar giant starsStellar abundancesR-processGalactic archaeologyMilky Way stellar halo |
| spellingShingle | Yangming Lin Haining Li Ruizheng Jiang Wako Aoki Satoshi Honda Zhenyu He Ruizhi Zhang Zhuohan Li Gang Zhao An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus The Astrophysical Journal Letters Chemically peculiar giant stars Stellar abundances R-process Galactic archaeology Milky Way stellar halo |
| title | An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus |
| title_full | An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus |
| title_fullStr | An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus |
| title_full_unstemmed | An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus |
| title_short | An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus |
| title_sort | actinide boost star discovered in the gaia sausage enceladus |
| topic | Chemically peculiar giant stars Stellar abundances R-process Galactic archaeology Milky Way stellar halo |
| url | https://doi.org/10.3847/2041-8213/adc8a3 |
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