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An $r$-process enhanced star in the dwarf galaxy Tucana III

Abstract : Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES J235532.66$-$593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the $r$-process and can be classified as an $r$-I star. DES J235532 is the first $r$-I star to be discovered in an ultra-faint satellite, and Tuc III is the second extremely low-luminosity system found to contain $r$-process enriched material, after Reticulum II. Comparison of the abundance pattern of DES J235532 with $r$-I and $r$-II stars found in other dwarf galaxies and in the Milky Way halo suggests a common astrophysical origin for the neutron-capture elements seen in all $r$-process enhanced stars. We explore both internal and external scenarios for the $r$-process enrichment of Tuc III and show that with abundance patterns for additional stars it should be possible to distinguish between them.
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Submitted on : Monday, July 3, 2017 - 6:25:25 PM
Last modification on : Tuesday, October 19, 2021 - 7:01:42 PM

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T.T. Hansen, J.D. Simon, J.L. Marshall, T.S. Li, D. Carollo, et al.. An $r$-process enhanced star in the dwarf galaxy Tucana III. Astrophys.J., 2017, 838 (1), pp.44. ⟨10.3847/1538-4357/aa634a⟩. ⟨hal-01554892⟩



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