Atomic transition probabilities for UV and blue lines of Fe II and abundance determinations in the photospheres of the Sun and metal-poor star HD 84937

TL;DR

This study provides new atomic transition probabilities for Fe II UV and blue lines, enabling more accurate iron abundance measurements in the Sun and a metal-poor star, HD 84937.

Contribution

It reports new branching fractions and transition probabilities for Fe II lines, improving atomic data for astrophysical abundance analyses.

Findings

Consistent solar Fe abundance of 7.46 +/- 0.03 from eight blue lines.

Fe abundance in HD 84937 determined as 5.26 +/- 0.01, aligning with previous estimates.

New atomic data enhances accuracy of stellar iron abundance measurements.

Abstract

We report new branching fractions for 121 UV lines from the low-lying odd-parity levels of Fe II belonging to the z6Do, z6Fo, z6Po, z4Fo, z4Do and z4Po terms of the 3d6(5D)4p configuration. These lines range in wavelength from 2250 - 3280 {\AA} and originate in levels ranging in energy from 38459 - 47626 cm-1. In addition, we report branching fractions for 10 weak blue lines connecting to the z4Do term which range in wavelength from 4173 - 4584 {\AA}. The BFs are combined with radiative lifetimes from the literature to determine transition probabilities and log(gf) values. Comparison is made to selected experimental and theoretical data from the literature. Our new data are applied to iron abundance determinations in the Sun and in metal-poor star HD 84937. For the Sun, eight blue lines yield log {\epsilon}(Fe) = 7.46 +/- 0.03, in agreement with standard solar abundance estimates. For HD 84937 the observable wavelength range extends to the vacuum UV ({\lambda} >= 2327 {\AA}), and from 75 lines we derive log {\epsilon}(Fe) = 5.26 +/- 0.01 ({\sigma} = 0.07), near to the metallicity estimates of past HD 84937 studies.