Observational constraints on the origin of the elements. VII. NLTE analysis of Y II lines in spectra of cool stars and implications for Y as a Galactic chemical clock

• DOI: 10.48550/arxiv.2308.12092
• Publication Date: 2023-01-01
• Authors: Nicholas Storm; M. Bergemann
• Keywords: Surface gravity

Yttrium (Y), a key s-process element, is commonly used in nucleosynthesis studies and as Galactic chemical clock when combined with magnesium (Mg). We study the applicability of previously assumed LTE line formation assumption Y abundance main-sequence red giant stars, probe impact NLTE effects on [Y/Mg] ratio, proposed stellar age indicator. derive parameters, ages, abundances Fe, Mg, for 48 solar analogue stars from high-resolution spectra acquired within Gaia-ESO survey. For Y, we present new atomic model. determine A(Y)$_{\rm NLTE}=2.12\pm0.04$ dex, $0.04$ dex higher than LTE. are modest optical II lines, which frequently Sun-like diagnostics. has small ratio such stars. metal-poor giants, lines substantial, potentially exceeding $+0.5$ dex. Gaia/4MOST/WEAVE benchmark star, HD 122563, find [Y/Fe]$_{\rm NLTE}=-0.55\pm0.04$ consistent obtained different lines. differential effect diagnostics late-type They notably affect giants very typical enrichment tracers neutron-capture elements. diagnostic remain minimal across metallicities. This affirms ratio's reliability cosmochronometer