NLTE analysis of Sr lines

Bergemann, M. (1), Hansen, C. J. (2) Bautista, M. (3) and Ruchti, G. (4) ((1) Max-Planck Institute for Astrophysics, Karl-Schwarzschild Str. 1, 85741, Garching, Germany; (2) Landessternwarte, Königstuhl 12, 69117, Heidelberg, Germany; (3) Department of Physics, Western Michigan University, Kalamazoo, MI, 49008, USA; (4)Max-Planck Institute for Astrophysics, Karl-Schwarzschild Str. 1, 85741, Garching, Germany)

We investigate the statistical equilibrium of neutral and singly-ionized strontium in late-type stellar atmospheres. Particular attention is given to the completeness of the model atom, which includes new energy levels, transition probabilities, photoionization and electron-impact excitation cross-sections computed with the R-matrix method. The NLTE model is applied to the analysis of SrI and SrII lines in the spectra of the Sun, Procyon, Arcturus, and HD 122563, showing a significant improvement in the ionization balance compared to LTE line formation calculations, which predict abundance discrepancies of up to 0.5dex. The solar Sr abundance is log(epsilon)=2.93+/-0.04dex, in agreement with the meteorites. We present the grid of NLTE abundance corrections for SrI and SrII lines that covers a wide range of stellar parameters.

 
See complete preprint –> http://adsabs.harvard.edu/abs/2012yCat..35469090B

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