%0 Journal Article
%T TOPoS. V. Abundance ratios in a sample of very metal-poor turn-off stars
%+ Galaxies, Etoiles, Physique, Instrumentation (GEPI)
%+ Institut de Biologie du Développement de Marseille (IBDM)
%+ Zentrum für Astronomie der Universität Heidelberg (ZAH)
%+ Istituto Nazionale di Fisica Nucleare, Sezione di Milano (INFN)
%+ Laboratoire Univers et Particules de Montpellier (LUPM)
%+ Leibniz-Institut für Astrophysik Potsdam (AIP)
%A François, P.
%A Caffau, E.
%A Bonifacio, P.
%A Spite, M.
%A Spite, F.
%A Cayrel, R.
%A Christlieb, N.
%A Gallagher, A.
%A Klessen, R.
%A Koch, A.
%A Ludwig, H.-G.
%A Monaco, L.
%A Plez, B.
%A Steffen, M.
%A Zaggia, S.
%< avec comité de lecture
%Z OBSPM-POP-22242
%Z OBSPM-POP-REVUE-36
%@ 0004-6361
%J Astronomy and Astrophysics - A&A
%I EDP Sciences
%V 620
%P A187
%8 2018-12
%D 2018
%Z 1811.00035
%Z 2018A&A...620A.187F
%R 10.1051/0004-6361/201834375
%K stars: abundances
%K Galaxy: abundances
%K stars: abundances
%Z Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]
%Z Physics [physics]/Astrophysics [astro-ph]Journal articles
%X Context. Extremely metal-poor stars are keys to understand the early evolution of our Galaxy. The ESO large programme TOPoS has been tailored to analyse a new set of metal-poor turn-off stars, whereas most of the previously known extremely metal-poor stars are giant stars.Aims. Sixty five turn-off stars (preselected from SDSS spectra) have been observed with the X-shooter spectrograph at the ESO VLT Unit Telescope 2, to derive accurate and detailed abundances of magnesium, silicon, calcium, iron, strontium and barium.Methods. We analysed medium-resolution spectra (R ≃ 10 000) obtained with the ESO X-shooter spectrograph and computed the abundances of several α and neutron-capture elements using standard one-dimensional local thermodynamic equilibrium (1D LTE) model atmospheres.Results. Our results confirms the super-solar [Mg/Fe] and [Ca/Fe] ratios in metal-poor turn-off stars as observed in metal-poor giant stars. We found a significant spread of the [α/Fe] ratios with several stars showing subsolar [Ca/Fe] ratios. We could measure the abundance of strontium in 12 stars of the sample, leading to abundance ratios [Sr/Fe] around the Solar value. We detected barium in two stars of the sample. One of the stars (SDSS J114424−004658) shows both very high [Ba/Fe] and [Sr/Fe] abundance ratios (>1 dex).
%G English
%2 https://hal.science/hal-02104754/document
%2 https://hal.science/hal-02104754/file/aa34375-18.pdf
%L hal-02104754
%U https://hal.science/hal-02104754
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