NLTE analysis of Sr lines in spectra of late-type stars with new R-matrix atomic data

TL;DR

This paper presents a detailed NLTE analysis of strontium lines in late-type star spectra, utilizing new atomic data from R-matrix calculations to improve abundance determinations.

Contribution

It introduces an enhanced NLTE model atom for Sr using new atomic data, improving ionization balance and abundance accuracy in stellar spectra analysis.

Findings

NLTE modeling reduces abundance discrepancies up to 0.5 dex.

Solar Sr abundance matches meteorite data.

Provides a comprehensive grid of NLTE corrections for various stellar parameters.

Abstract

We investigate 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 Sr I and Sr II 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 0.5 dex. The solar Sr abundance is log A = 2.93 \pm 0.04 dex, in agreement with the meteorites. A grid of NLTE abundance corrections for Sr I and Sr II lines covering a large range of stellar parameters is presented.