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

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

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Título Sc and neutron-capture abundances in Galactic low- and high-α field halo stars
Autor Fishlock, Cherie K.
Yong, David
Karakas, Amanda I.
Alves-Brito, Alan
Meléndez, Jorge
Nissen, Poul Erik
Kobayashi, Chiaki
Casey, Andrew Raithby
Abstract 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-α halo and thick-disc stars) based on the [α/Fe] abundance ratio and their kinematics as discovered by Nissen & Schuster. We find differences between the low- and high-α 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-α stars have a lower abundance compared to the high-α stars. The low-α 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-α 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-α population. By comparing the low-α population with AGB stellar models, we place constraints on the mass range of the AGB stars.
Contido em Monthly notices of the Royal Astronomical Society. Oxford. Vol. 466, no. 4 (May 2017), p. 4672–4682
Assunto Composicao estelar
Formacao de galaxias
Massa estelar
Metalicidade
[en] Galaxy: halo
[en] Stars: abundances
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/168956
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