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Journal Article

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

MPS-Authors

François,  P.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Caffau,  E.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Bonifacio,  P.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Spite,  M.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Spite,  F.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Cayrel,  R.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Christlieb,  N.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Gallagher,  A. J.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Klessen,  R.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Koch,  A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Ludwig,  H. -G.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Monaco,  L.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Plez,  B.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Steffen,  M.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Zaggia,  S.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

External Resource

https://ui.adsabs.harvard.edu/abs/2018A&A...620A.187F
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Citation

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.


Cite as: https://hdl.handle.net/21.11116/0000-0005-CDB8-5
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>