The R-Process Alliance: 2MASS J09544277+5246414, the most actinide-enhanced R-II star known
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Holmbeck_2018_ApJL_859_L24.pdf
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Author(s)
Frebel, Anna
Date Issued
June 2018
Journal
Astrophysical journal. Letters
Publisher
American Astronomical Society
Citation
Holmbeck, Erika M., et al., "The R-Process Alliance: 2MASS J09544277+5246414, the most actinide-enhanced R-II star known." Astrophysical journal. Letters 859, 2 (June 2018): letter 24 doi 10.3847/2041-8213/AAC722 ©2018 Author(s)
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Final published version
Abstract
We report the discovery of a new actinide-boost star, 2MASS J09544277+5246414, originally identified as a very bright (V = 10.1), extremely metal-poor ([Fe/H] = -2.99) K giant in the LAMOST survey, and found to be highly r-process-enhanced (r-II; [Eu/Fe] = +1.28]), during the snapshot phase of the R-Process Alliance (RPA). Based on a high signal-to-noise ratio (S/N), high-resolution spectrum obtained with the Harlan J. Smith 2.7 m telescope, this star is the first confirmed actinide-boost star found by RPA efforts. With an enhancement of [Th/Eu] = +0.37, 2MASS J09544277+5246414 is also the most actinide-enhanced r-II star yet discovered, and only the sixth metal-poor star with a measured uranium abundance ([U/Fe] = +1.40). Using the Th/U chronometer, we estimate an age of 13.0 ± 4.7 Gyr for this star. The unambiguous actinide-boost signature of this extremely metal-poor star, combined with additional r-process-enhanced and actinide-boost stars identified by the RPA, will provide strong constraints on the nature and origin of the r-process at early times. ©2018
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.3847/2041-8213/AAC722
