A New Technique for Determining Europium Abundances in Solar-Metallicity Stars

We present a new technique for measuring the abundance of europium, a representative r-process element, in solar-metallicity stars. Our algorithm compares LTE synthetic spectra with high-resolution observational spectra using a chi-square-minimization routine. The analysis is fully automated, and therefore allows consistent measurement of blended lines even across very large stellar samples. We compare our results with literature europium abundance measurements and find them to be consistent; we also find our method generates smaller errors.

💡 Research Summary

The paper introduces a fully automated method for determining europium (Eu) abundances in solar‑metallicity stars, addressing the limitations of traditional manual measurements that struggle with blended lines and large data sets. The authors generate LTE synthetic spectra using ATLAS9 model atmospheres tailored to each star’s effective temperature, surface gravity, and metallicity. A line list centered on the Eu II 4129 Å transition, supplemented by nearby Fe I/II and Ti I/II lines from the VALD database, is used to construct a 20 Å synthetic window. High‑resolution (R ≈ 60 000) and high‑signal‑to‑noise (S/N ≥ 100) spectra of roughly 500 solar‑metallicity stars serve as the observational input.

The core of the technique is a χ²‑minimization routine that compares the observed spectrum to a pre‑computed grid of synthetic spectra. First, the observed spectra are continuum‑normalized and a mask is applied to exclude regions of severe contamination. An initial Eu abundance estimate is obtained by locating the grid point with the lowest χ². A finer search around this point refines the Eu abundance and yields a statistical 1σ uncertainty. The entire pipeline is implemented in Python, leveraging parallel processing to handle dozens of stars simultaneously, thereby ensuring scalability to surveys containing thousands of targets.

Validation against literature values—most of which rely on manual equivalent‑width measurements or bespoke spectral synthesis—shows excellent agreement. The mean offset between the new method and published