Speaker
Description
Stellar ages remain one of the most difficult parameters to determine in astrophysics. Chemical clocks based on s-process–to–α element abundance ratios offer a promising alternative, but require a robust calibration. We derived asteroseismic ages for 218 F–K giant stars observed in and around the TESS Northern Continuous Viewing Zone using the PARAM and BASTA codes. High-resolution spectra obtained with the Vilnius University Echelle Spectrograph (VUES) mounted at the 1.65 m telescope of the Molėtai Astronomical Observatory (MAO) in Lithuania were used to determine Mg and Y abundances, including non-local thermodynamic equilibrium (NLTE) corrections.
We found that the [Y/Mg]–age relation shows a clear radial dependence across the Galactic disc. The outer disc exhibited the steepest trend and a systematically higher zero point, while progressively flatter relations were observed toward the inner disc and the thick disc. Thick-disc stars displayed an almost flat relation, confirming that [Y/Mg] is not a reliable age indicator for this population. These results robustly confirm that the [Y/Mg] clock is environment-dependent, reflects differences in star-formation efficiency and chemical enrichment histories, and establishes it as a valuable probe of Galactic chemical evolution.