TOPoS: V: Abundance ratios in a sample of very metal-poor turn-off stars
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. Sixty five turn-off stars (preselec...
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| Main Authors: | , , , , , |
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| Format: | Article (Journal) Chapter/Article |
| Language: | English |
| Published: |
31 Oct 2018
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| In: |
Arxiv
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| Online Access: | Verlag, Volltext: http://arxiv.org/abs/1811.00035
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| Author Notes: | P. François, E. Caffau, P. Bonifacio, M. Spite, F. Spite, R. Cayrel, N. Christlieb, A. J. Gallagher, R. Klessen, A. Koch, H.-G. Ludwig, L. Monaco, B. Plez, M. Steffen, and S. Zaggia |
| Summary: | 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. 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. We analysed medium-resolution spectra (R ~ 10 000) obtained with the ESO X-Shooter spectrograph and computed the abundances of several alpha and neutron-capture elements using standard one-dimensional local thermodynamic equilibrium (1D LTE) model atmospheres. 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 [alpha/Fe] ratios with several stars showing sub-solar [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). |
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| Item Description: | Gesehen am 16.10.2020 |
| Physical Description: | Online Resource |