摘要：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 (2015, A&A, 579, A52) 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 (0.3–10.0 Gyr) 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 (2015). 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 ~0.8 Gyr precision in the 0 to 10 Gyr
range.
