Improved Laboratory Transition Probabilities for Er II and Applications to the Erbium Abundances of the Sun and Five r-Process Rich, Metal-Poor Stars

TL;DR

This paper provides improved laboratory transition probabilities for Er II, enabling more accurate determinations of erbium abundances in the Sun and metal-poor stars, confirming the consistency of r-process nucleosynthesis patterns across different stellar environments.

Contribution

The study presents new, precise transition probabilities for Er II based on combined laser-induced fluorescence and Fourier transform spectrometry measurements, enhancing stellar abundance analyses.

Findings

Solar Er abundance matches meteoric values within uncertainties.

Revised Er abundances in metal-poor stars agree with solar-system r-process ratios.

Supports similar r-process nucleosynthesis patterns in early and later Galaxy stars.

Abstract

Recent radiative lifetime measurements accurate to +/- 5% (Stockett et al. 2007, J. Phys. B 40, 4529) using laser-induced fluorescence (LIF) on 8 even-parity and 62 odd-parity levels of Er II have been combined with new branching fractions measured using a Fourier transform spectrometer (FTS) to determine transition probabilities for 418 lines of Er II. This work moves Er II onto the growing list of rare earth spectra with extensive and accurate modern transition probability measurements using LIF plus FTS data. This improved laboratory data set has been used to determine a new solar photospheric Er abundance, log epsilon = 0.96 +/- 0.03 (sigma = 0.06 from 8 lines), a value in excellent agreement with the recommended meteoric abundance, log epsilon = 0.95 +/- 0.03. Revised Er abundances have also been derived for the r-process-rich metal-poor giant stars CS 22892-052, BD+17 3248, HD 221170, HD 115444, and CS 31082-001. For these five stars the average Er/Eu abundance ratio, <log epsilon (Er/Eu)> = 0.42, is in very good agreement with the solar-system r-process ratio. This study has further strengthened the finding that r-process nucleosynthesis in the early Galaxy which enriched these metal-poor stars yielded a very similar pattern to the r-process which enriched later stars including the Sun.