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arXiv · 2512.10003

Detailed Chemical Abundance Analysis of the Brightest Stars in the Turranburra and Willka Yaku Stellar Streams

Kaitlin B. Webber·Terese T. Hansen·Jennifer L. Marshall·Alexander P. Ji·Ting S. Li·Gary S. Da Costa·Lara R. Cullinane·Denis Erkal·Sergey E. Koposov·Kyler Kuehn·Geraint F. Lewis·Dougal Mackey·Sarah L. Martell·Andrew B. Pace·Nora Shipp·Jeffrey D. Simpson·Zhen Wan·Daniel B. Zucker·Victor A. Alvarado·Joss Bland-Hawthorn·Guilherme Limberg·Gustavo E. Medina·Sam A. Usman
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Abstract

We present a detailed chemical abundance analysis of the three brightest known stars from each of the Turranburra and Willka Yaku stellar streams using high-resolution Magellan/MIKE spectra. Abundances for 27 elements, ranging from carbon to dysprosium, were derived. Our results support the original classification that Turranburra, with a low average metallicity of $\mathrm{[Fe/H]=-2.45} \pm 0.07$, likely originates from a dwarf-galaxy progenitor. Willka Yaku has a low average metallicity of $\mathrm{[Fe/H]=-2.35 \pm 0.03}$ with a small scatter in the abundances, consistent with a globular cluster progenitor as suggested by previous studies. Both streams exhibit mild enhancements in neutron-capture elements, with averages of $\mathrm{[Eu II/Fe]}=$ $0.47 \pm{0.09}$ for Turranburra and $0.44 \pm{0.05}$ for Willka Yaku, consistent with enrichment from an $r$-process event. A similar enrichment is observed in other stellar streams, and we further discuss this signature as it relates to the potential enrichment histories of these two streams.

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Kaitlin B. Webber, Terese T. Hansen, Jennifer L. Marshall, Alexander P. Ji, Ting S. Li, Gary S. Da Costa, Lara R. Cullinane, Denis Erkal, Sergey E. Koposov, Kyler Kuehn, Geraint F. Lewis, Dougal Mackey, Sarah L. Martell, Andrew B. Pace, Nora Shipp, Jeffrey D. Simpson, Zhen Wan, Daniel B. Zucker, Victor A. Alvarado, Joss Bland-Hawthorn, Guilherme Limberg, Gustavo E. Medina, Sam A. Usman. 2025-12-10. Detailed Chemical Abundance Analysis of the Brightest Stars in the Turranburra and Willka Yaku Stellar Streams. https://arxiv.org/abs/2512.10003

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