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  TOPoS. V. Abundance ratios in a sample of very metal-poor turn-off stars

François, P., Caffau, E., Bonifacio, P., Spite, M., Spite, F., Cayrel, R., et al. (2018). TOPoS. V. Abundance ratios in a sample of very metal-poor turn-off stars. Astronomy and Astrophysics, 620.

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Item Permalink: https://hdl.handle.net/21.11116/0000-0005-CDB8-5 Version Permalink: https://hdl.handle.net/21.11116/0000-0005-CDB9-4
Genre: Journal Article

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https://ui.adsabs.harvard.edu/abs/2018A&A...620A.187F (Any fulltext)
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 Creators:
François, P.1, Author
Caffau, E.1, Author
Bonifacio, P.1, Author
Spite, M.1, Author
Spite, F.1, Author
Cayrel, R.1, Author
Christlieb, N.1, Author
Gallagher, A. J.1, Author
Klessen, R.1, Author
Koch, A.1, Author
Ludwig, H. -G.1, Author
Monaco, L.1, Author
Plez, B.1, Author
Steffen, M.1, Author
Zaggia, S.1, Author
Affiliations:
1Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners, ou_2421692              

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Free keywords: stars: abundances Galaxy: abundances Astrophysics - Solar and Stellar Astrophysics
 Abstract: 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 (&gt;1 dex). Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme ID 189.D-0165.Equivalent widths of the Fe lines are only, and Tables A.1 and A.2 are also available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/620/A187">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/620/A187</A>

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 Dates: 2018
 Publication Status: Issued
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Title: Astronomy and Astrophysics
Source Genre: Journal
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Pages: - Volume / Issue: 620 Sequence Number: - Start / End Page: - Identifier: -