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        Elevated r-process enrichment in Gaia Sausage and Sequoia

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        2012.01430v1.pdf (PDF, 2Mb)
        Author
        Aguado, David S.
        Belokurov, Vasily
        Myeong, G. C.
        Evans, N. Wyn
        Kobayashi, Chiaki
        Sbordone, Luca
        Chanamé, Julio
        Navarrete, Camila
        Koposov, Sergey E.
        Attention
        2299/24419
        Abstract
        The Gaia Sausage and the Sequoia represent the major accretion events that formed the stellar halo of the Milky Way. A detailed chemical study of these main building blocks provides a pristine view of the early steps of the Galaxy's assembly. We present the results of the analysis of the UVES high-resolution spectroscopic observations at the 8.2m VLT of 9 Sausage/Sequoia members selected kinematically using Gaia DR2. We season this set of measurements with archival data from Nissen & Schuster (2011) and GALAH DR3 (2020). Here, we focus on the neutron-capture process by analysing Sr, Y, Ba and Eu behavior. We detect clear enhancement in Eu abundance ([Eu/Fe]~0.6-0.7) indicative of large prevalence of r-process in the stellar n-capture makeup. We are also able to trace the evolution of the heavy element production across a wide range of metallicity. Barium to europium ratio changes from a tight, flat sequence with [Ba/Eu]=-0.7 reflecting dominant core-collapse SNe contribution, to a clear upturn at higher iron abundances, betraying the onset of contamination from asymptotic giant branch (AGB) ejecta. Additionally, we discover two clear sequences in [Fe/H]-[Ba/Fe] plane likely caused by distinct levels of s-process pollution and mixing within the GS progenitor.
        Publication date
        2021-02-10
        Published in
        The Astrophysical Journal
        Published version
        https://doi.org/10.3847/2041-8213/abdbb8
        Other links
        http://hdl.handle.net/2299/24419
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