2016A&A...590A..32T

Context. Solar twins are stars with similar stellar (surface) parameters to the Sun that can have a wide range of ages. This provides an opportunity to analyze the variation of their chemical abundances with age. Nissen (2015A&A...579A..52N) recently suggested that the abundances of the s-process element Y and the α-element Mg could be used to estimate stellar ages.
Aims. This paper aims to determine with high precision the Y, Mg, and Fe abundances for a sample of 88 solar twins that span a broad age range (0.3-10.0Gyr) and investigate their use for estimating ages.
Methods. We obtained high-quality Magellan Inamori Kyocera Echelle (MIKE) spectra and determined Y and Mg abundances using equivalent widths and a line-by-line differential method within a 1D LTE framework. Stellar parameters and iron abundances were measured in Paper I of this series for all stars, but a few (three) required a small revision.
Results. The [Y/Mg] ratio shows a strong correlation with age. It has a slope of -0.041±0.001 dex/Gyr and a significance of 41σ. This is in excellent agreement with the relation first proposed by Nissen (2015A&A...579A..52N). We found some outliers that turned out to be binaries where mass transfer may have enhanced the yttrium abundance. Given a precise measurement of [Y/Mg] with typical error of 0.02 dex in solar twins, our formula can be used to determine a stellar age with ∼0.8Gyr precision in the 0 to 10Gyr range.