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Galactic evolution of copper in the light of NLTE computations

Abstract We have developed a model atom for Cu with which we perform statistical equilibrium computations that allow us to compute the line formation of Cu i lines in stellar atmospheres without assuming local thermodynamic equilibrium (LTE). We validate this model atom by reproducing the observed l...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2018-01, Vol.473 (3), p.3377-3384
Main Authors: Andrievsky, S., Bonifacio, P., Caffau, E., Korotin, S., Spite, M., Spite, F., Sbordone, L., Zhukova, A. V.
Format: Article
Language:English
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Summary:Abstract We have developed a model atom for Cu with which we perform statistical equilibrium computations that allow us to compute the line formation of Cu i lines in stellar atmospheres without assuming local thermodynamic equilibrium (LTE). We validate this model atom by reproducing the observed line profiles of the Sun, Procyon and 11 metal-poor stars. Our sample of stars includes both dwarfs and giants. Over a wide range of stellar parameters, we obtain excellent agreement among different Cu i lines. The 11 metal-poor stars have iron abundances in the range − 4.2 ≤ [Fe/H] ≤ -1.4, the weighted mean of the [Cu/Fe] ratios is −0.22 dex, with a scatter of −0.15 dex. This is very different from the results from LTE analysis (the difference between NLTE and LTE abundances reaches 1  dex) and in spite of the small size of our sample, it prompts for a revision of the Galactic evolution of Cu.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stx2526