Both accurate and precise gf-values for FeII lines

TL;DR

This paper provides a new set of oscillator strengths for FeII lines that are both accurate and precise, validated through high-quality stellar spectra, improving iron abundance measurements in stars.

Contribution

The authors introduce a new line list of FeII oscillator strengths combining laboratory normalization and theoretical calculations, enhancing accuracy and precision in stellar spectroscopy.

Findings

FeII gf-values are accurate and precise.

Line-to-line scatter in FeII-based iron abundances is very low.

Solar iron abundance measured as A_Fe = 7.45 using these gf-values.

Abstract

We present a new set of oscillator strengths for 142 FeII lines in the wavelength range 4000-8000 A. Our gf-values are both accurate and precise, because each multiplet was globally normalized using laboratory data (accuracy), while the relative gf-values of individual lines within a given multiplet were obtained from theoretical calculations (precision). Our line list was tested with the Sun and high-resolution (R ~ 10^5), high-S/N (~700-900) Keck+HIRES spectra of the metal-poor stars HD 148816 and HD 140283, for which line-to-line scatter (sigma) in the iron abundances from FeII lines as low as 0.03, 0.04, and 0.05 dex are found, respectively. For these three stars the standard error in the mean iron abundance from FeII lines is negligible (sigma_mean <= 0.01 dex). The mean solar iron abundance obtained using our gf-values and different model atmospheres is A_Fe = 7.45 (sigma = 0.02).