Both accurate and precise gf-values for Fe II lines

Abstract

We present a new set of oscillator strengths for 142 Fe ii lines in the wavelength range 4000-8000 Å. Our g f -values are both accurate and precise, because each multiplet was globally normalized using laboratory data (accuracy), while the relative g f -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 ≈ 105), high-S/N (≈700-900) Keck+HIRES spectra of the metal-poor stars HD 148816 and HD 140283, for which line-to-line scatter (σ) in the iron abundances from Fe ii 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 Fe ii lines is negligible (σmean ≤ 0.01 dex). The mean solar iron abundance obtained using our g f -values and different model atmospheres is AFe = 7.45(σ = 0.02). © ESO 2009.