Proc. IAU volume 13, issue S334, P259-262 2017 DOI: 10.1017/s1743921317007177 View full text
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Rana Ezzeddine, Tatyana Sitnova, Anna Frebel, Lyudmilla Mashonkina, Bertrand Plez

Abstract: AbstractWe present Non-Local Thermodynamic Equilibrium (Non-LTE) abundance corrections for Mg, Ca, and Fe in 12 ultra metal-poor (UMP) stars ([Fe/H] < −4.00). We show that they increase in absolute value toward the lower metallicity up to 0.45 dex for Mg, 0.30 dex for Ca, and 1.00 dex for Fe. This represents a first step toward a full Non-LTE analysis of chemical species in the UMP stars that will enable us to put useful constraints on the properties of the “First” stars.