Tracing the Milky Way: calibrating chemical ages with high-precision Kepler data

Chemical clocks offer a powerful tool for estimating stellar ages from spectroscopic surveys. We present a new detailed spectroscopic analysis of 68 Kepler red giant stars to provide a suite of high-precision abundances along with asteroseismic ages with better than 10 per cent precision from individual mode frequencies. We obtained several chemical clocks as ratios between s-process elements (Y, Zr, Ba, La, and Ce) and α-elements (Mg, Ca, Si, Al, and Ti). Our data show that [Ce/Mg] and [Zr/Ti] display a remarkably tight correlation with stellar ages, with abundance dispersions of 0.08 and 0.01 dex, respectively, and below 3 Gyr in ages, across the entire Galactic chronochemical history. While improving the precision floor of spectroscopic surveys is critical for broadening the scope and applicability of chemical clocks, the intrinsic accuracy of our relations – enabled by high-resolution chemical abundances and stellar ages in our sample – allows us to draw meaningful conclusions about age trends across stellar populations. By applying our relations to the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and Gaia-ESO surveys, we are able to differentiate the low- and high-α sequences in age, recover the age–metallicity relation, observe the disc flaring of the Milky Way, and identify a population of old metal-rich stars.