Is [Y/Mg] a Reliable Age Diagnostic for FGK Stars?

Abstract

Current spectroscopic surveys are producing large catalogs of chemical abundances for stars of all types. The yttrium to magnesium ratio, [Y/Mg], has emerged as a candidate age indicator for solar twins in the local stellar neighborhood. However, it is unclear whether it is a viable age diagnostic for more diverse stellar types, so we investigate [Y/Mg] as an age indicator for the FGK-type planet host stars observed by $Kepler$. We find that the [Y/Mg] "Clock" is most precise for solar twins, with a [Y/Mg]/Age slope of $m$ = $-$0.0370 $\pm$ 0.0071 dex/Gyr and ${\sigma }_{\mathrm{Age}}$ = 2.6 Gyr. We attribute the lower precision compared to literature results to non-solar twins contaminating our solar twin sample and recommend a 1.5 Gyr systematic uncertainty for stellar ages derived with any [Y/Mg]-Age relation. We also analyzed the [Y/Mg] Clock as a function of $T_{\mathrm{eff}}$, $\log g$, and metallicity individually and find no strong trends, but compute statistically significant [Y/Mg]-Age relations for subsamples defined by ranges in $T_{\mathrm{eff}}$, $\log g$, and metallicity. Finally, we compare [Y/Mg] and rotation ages and find statistically similar trends as for isochrone ages, although we find that rotation ages perform better for GK dwarfs while isochrones perform better for FG subgiants. We conclude that the [Y/Mg] Clock is most precise for solar twins and analogs but is also a useful age diagnostic for FGK stars.

18 pages, 13 figures, 2 tables. Accepted by ApJ

References in corpus (26)

• Array Programming with NumPy
• The Dartmouth Stellar Evolution Database
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Correcting stellar oscillation frequencies for near-surface effects
• High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature
• The Kepler Follow-Up Observation Program. I. A Catalog of Companions to Kepler Stars from High-Resolution Imaging
• Inferring probabilistic stellar rotation periods using Gaussian processes
• The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample
• The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
• Lithium Depletion of Nearby Young Stellar Associations
• Surface rotation and photometric activity for Kepler targets. II. G and F main-sequence stars, and cool subgiant stars
• A Temporary Epoch of Stalled Spin-Down for Low-Mass Stars: Insights from NGC 6811 with Gaia and Kepler
• Abundance to age ratios in the HARPS-GTO sample with Gaia DR2: Chemical clocks for a range of [Fe/H]
• On the kinematic evolution of young local associations and the Sco-Cen complex
• High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends of element ratios with stellar age
• On the metallicity dependance of the [Y/Mg] - age relation for solar type stars
• High-precision abundances of elements in Kepler LEGACY stars. Verification of trends with stellar age
• Accurate Gravities of F, G, and K stars from High Resolution Spectra Without External Constraints
• Chemical Evolution in the Milky Way: Rotation-based ages for APOGEE-Kepler cool dwarf stars
• Study of Lithium Rich Giants with the GALAH Spectroscopic Survey
• The Gaia-ESO Survey: Age-chemical-clock relations spatially resolved in the Galactic disc
• Constraining the evolution of stellar rotation using solar twins
• Exploring the evolution of stellar rotation using Galactic kinematics
• Boron Abundances Across the "Li-Be Dip" in the Hyades
• Further Evidence of Modified Spin-down in Sun-like Stars: Pileups in the Temperature-Period Distribution
• The [Y/Mg] clock works for evolved solar metallicity stars