Gaia FGK Benchmark Stars: Selecting Infrared Lines for Abundance Determination

Abstract

The advent of new and more powerful infrared spectrographs has significantly motivated the advancement of the study of atomic and molecular line lists and stellar atmosphere models. While optical abundance determinations rely on extensively validated line lists and modeling frameworks, infrared measurements still face larger uncertainties, largely driven by the choice of atmospheric models and the quality of the available atomic data. In this work, we aim to deliver a homogeneous and reproducible set of atomic absorption lines in the Y, J, and H bands (9800 - 18000 (Angstrom)), based exclusively on laboratory atomic data. We analyse CRIRES spectra of six Gaia FGK Benchmark Stars spanning a wide range in effective temperature, surface gravity, and chemical composition. Synthetic spectra are computed using the benchmark stellar parameters, and each transition is evaluated independently in every star through a quantitative sequence that examines line depth, saturation, blending (purity), and the agreement between observed and synthetic line profiles. We identify a set of robust atomic transitions in these bands that remain consistent across the full range of stellar parameters represented in our sample. Lines of alpha-elements such as Mg I, Si I, and Ca I, together with several Fe I transitions, satisfy all robustness criteria. Among the neutron-capture species explored, only Sr II provides lines that consistently meet our requirements. Beyond the specific list of accepted transitions, this study demonstrates that a fully quantitative, multi-criteria framework provides a transparent and reproducible foundation for near-infrared line validation as laboratory data, stellar atmosphere models, and instrumentation continue to improve.

22 pages, 7 figures

References in corpus (19)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• The James Webb Space Telescope Mission
• The APOGEE red-clump catalog: Precise distances, velocities, and high-resolution elemental abundances over a large area of the Milky Way's disk
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• Atomic data for the Gaia-ESO Survey
• Sulphur and zinc abundances in Galactic halo stars revisited
• The APOGEE Data Release 16 Spectral Line List
• Correcting for Telluric Absorption: Methods, Case Studies, and Release of the TelFit Code
• The GALAH Survey: Non-LTE departure coefficients for large spectroscopic surveys
• CRIRES${}^{+}$ on sky at the ESO Very Large Telescope
• Abundances in bulge stars from high-resolution, near-IR spectra I. The CNO elements observed during the science verification of CRIRES at VLT
• FeI lines in 0.91-1.33 $\mu$m spectra of red giants for measuring the microturbulence and metallicities
• Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra
• Determination of small-scale magnetic fields on Sun-like stars in the near-infrared using CRIRES${}^{+}$
• Identification of Absorption Lines of Heavy Metals in the Wavelength Range 0.97--1.32 Micron
• Gaia FGK Benchmark Stars: spectral library, metallicities and abundances of $\alpha$ and Fe-peak elements of the third version
• A First Study of Giant Stars in the Galactic Bulge based on Crires spectra