University of Hertfordshire

From the same journal

From the same journal

By the same authors

Elevated r-process enrichment in Gaia Sausage and Sequoia

Research output: Contribution to journalArticlepeer-review


  • 2012.01430v1

    Accepted author manuscript, 2.09 MB, PDF document

  • David S. Aguado
  • Vasily Belokurov
  • G. C. Myeong
  • N. Wyn Evans
  • Chiaki Kobayashi
  • Luca Sbordone
  • Julio Chanamé
  • Camila Navarrete
  • Sergey E. Koposov
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Original languageEnglish
Article numberL8
JournalThe Astrophysical Journal
Publication statusPublished - 10 Feb 2021


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.


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