Sc and neutron-capture abundances in Galactic low- and high-alpha field halo stars

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DOI

    Cherie K. Fishlock, RSPAS, Australian National University, D. Yong, RSPAS, Australian National University, Amanda I. Karakas, Monash University, Alan Alves Brito, Universidade Federal do Rio Grande do Sul, J. Meléndez, Universidade de São Paulo,
  • P. E. Nissen
  • C. Kobayashi, University of Hertfordshire, A. R. Casey, Cambridge University

We determine relative abundance ratios for the neutron-capture elements Zr, La, Ce, Nd and Eu for a sample of 27 Galactic dwarf stars with -1.5 <[Fe/H] <-0.8. We also measure the iron-peak element Sc. These stars separate into three populations (low-and high-a halo and thick-disc stars) based on the [alpha/Fe] abundance ratio and their kinematics as discovered by Nissen & Schuster. We find differences between the low-and high-alpha groups in the abundance ratios of [Sc/Fe], [Zr/Fe], [La/Zr], [Y/Eu] and [Ba/Eu] when including Y and Ba from Nissen & Schuster. For all ratios except [La/Zr], the low-alpha stars have a lower abundance compared to the high-alpha stars. The low-alpha stars display the same abundance patterns of high [Ba/Y] and low [Y/Eu] as observed in present-day dwarf spheroidal galaxies, although with smaller abundance differences, when compared to the high-alpha stars. These distinct chemical patterns have been attributed to differences in the star formation rate between the two populations and the contribution of low-metallicity, low-mass asymptotic giant branch (AGB) stars to the low-alpha population. By comparing the low-alpha population with AGB stellar models, we place constraints on the mass range of the AGB stars.

Original languageEnglish
JournalRoyal Astronomical Society. Monthly Notices
Volume466
Issue number4
Pages (from-to)4672-4682
Number of pages11
ISSN0035-8711
DOIs
StatePublished - May 2017

    Research areas

  • stars: abundances, Galaxy: halo, ASYMPTOTIC GIANT BRANCH, METAL-POOR STARS, DWARF SPHEROIDAL GALAXIES, CHEMICAL EVOLUTION, R-PROCESS, LOW-METALLICITY, GLOBULAR-CLUSTER, MASSIVE STARS, OLD STARS, MILKY-WAY

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