Traits for chemical evolution in solar twins: Trends of neutron-capture elements with stellar age

TL;DR

This study identifies abundance ratios involving neutron-capture elements in solar twins that vary linearly with stellar age, providing new constraints on chemical evolution models of the Milky Way.

Contribution

It systematically finds abundance ratios with linear age trends, highlighting the importance of s-process elements as references in chemical evolution studies.

Findings

55 abundance ratios show linear trends with age

[C/Ba] has the strongest age dependency with a slope of 0.049 dex/Gyr

Using neutron-capture elements as references can improve chemical evolution models

Abstract

The physical processes driving chemical evolution in the Milky Way can be probed using the distribution of abundances in low-mass FGK type stars in space phase at different times. During their final stages of evolution stars experience nucleosynthesis several times, each at different timescales and producing different chemical elements, so finding abundance ratios that have simple variations across cosmic times remains a challenge. Using the sample of 80 solar twins for which ages and abundances of 30 elements were measured with high precision by Bedell et al 2018, we searched for all possible abundance ratios combinations that show linear trends with age. We found 55 such ratios, all combining a neutron-capture element and another one produced by different nucleosynthesis channels. We recovered the ratios of [Y/Mg], [Ba/Mg] and [Al/Y] reported previously in the literature, and found that [C/Ba] had the largest dependency with age with a slope of $0.049 \pm 0.003~\mathrm{dex/Gyr}$, imposing constraints on the magnitude of time dependency of abundance ratios in solar twins. Our results suggest using s-process elements, in lieu of Fe, as a reference for constraining chemical evolution models of the solar neighbourhood. Our study illustrates hows a large variety of chemical elements measured from high resolution spectra is key in facing current challenges in understanding the formation and evolution of our Galaxy.