Asteroseismic ages for 17,000 stars in Kepler, K2 and TESS

TL;DR

This work delivers homogeneous asteroseismic ages and orbital parameters for over 17,000 red giants by integrating Kepler, K2, and TESS photometry with Gaia DR3 astrometry and APOGEE/GALAH spectroscopy. Using PARAM with a MESA-based model grid, the authors explore how choices of seismic constraints ($ u_{max}$ vs. $L$) and parallax zero-points affect inferred masses, radii, and ages, and they apply stringent reliability flags to mitigate biases, particularly for K2 data. The catalog enables detailed chrono-chem-kinematic studies across Galactic regions, including the analysis of [$oldsymbol{ m abla}$/Fe/H] sequences, ex situ populations, and mass–[C/N] relations, while also providing chemical clocks based on multiple elemental abundances. These results advance Galactic archaeology by supplying a vast, well-characterized training set for age inference and by highlighting systematic uncertainties tied to observational constraints and priors. The dataset will support ongoing and future analyses with PLATO and other surveys, as well as machine-learning age estimations.

Abstract

The availability of asteroseismic constraints for tens of thousands of red giant (RG) stars has opened the door to robust age estimates, enabling time-resolved studies of different populations of stars in the Milky Way. This study leverages data from Kepler, K2, and TESS, in conjunction with astrometric data from Gaia DR3 and spectroscopic constraints from APOGEE DR17 and GALAH DR3, to infer parameters for over 17,000 RGs. We use the code PARAM to homogeneously infer stellar properties considering in detail the sensitivity of our results to different choices of observational constraints. We focus on age estimation, identifying potentially unreliable age determinations, and highlight stars with unreliable $Δν$ measurements based on comparisons using Gaia luminosities. These are particularly relevant in K2 data due to the short duration of the observations of each campaign, and therefore important to characterise for Galactic archaeology studies where the spatial range of K2 is a benefit. Thanks to the combination of data from different missions we explore trends in age, mass, and orbital parameters such as $R_\mathrm{g}$ and $Z_\mathrm{max}$, and examine time-resolved [$α$/M]-[Fe/H] planes across different Galactic regions. Additionally, we compare age distributions in low- and high-$α$ populations and chemically selected ex situ stars. The study also extends known mass-[C/N] ratio relationships to lower masses. The catalogues resulting from this work will be instrumental in addressing key questions in Galactic archaeology and stellar evolution, and to improve training sets for machine-learning-based age estimations.

Figures (27)

• Figure 1: Location of stars in our samples in Galactic coordinates. Green, blue and orange points show stars with reliable ages from Kepler, K2 and TESS, respectively. Stars with reliable data but ages which do not pass our tests are shown with red points. In this figure we use distances from PARAM and reliability tests based on $\Delta\nu$. This figure was generated using mwplot$^\mathrm{a}$, and the image in the background is modified from an image by ESA/Gaia/DPAC. $^\mathrm{a}$https://milkyway-plot.readthedocs.io/en/latest/index.html
• Figure 2: Location of stars in our sample in left-handed Galactocentric coordinates (top) and Galactocentric cylindrical coordinates (bottom). The colours are the same as Figure \ref{['fig:sky_pos']}. In this figure we use distances from PARAM and reliability tests based on $\Delta\nu$.
• Figure 3: Average $\alpha$ element abundance [$\alpha$/M] for APOGEE samples or [$\alpha$/Fe] for the GALAH sample vs. [Fe/H]. The grey lines show the division between high-, low- and intermediate $\alpha$ populations used in Section \ref{['sec:app_chemistry']}. We have used reliability tests based on $\Delta\nu$ and the colours are the same as Figure \ref{['fig:sky_pos']}.
• Figure 4: Stellar mass vs. radius for K2 stars from scaling relations where $\Delta\nu$ (top, Equations \ref{['eq:M_Dnu']} and \ref{['eq:R_Dnu']}) or $L$ (bottom, Equations \ref{['eq:M_L']} and \ref{['eq:R_L']}) are used as an observational constraint. Stars flagged for unreliable $\Delta\nu$ are shown in red (see Section \ref{['sssec:Dnu_L']} for a description of the flag). The large black points in the top panel show the effect of decreasing $\Delta\nu$ in steps of 5% and recalculating the mass and radius, for a star of initial mass $\qty[]{1}{\solarmass}{}{}$ and radius $\qty[]{11}{\solarradius}{}{}$. Stellar mass and radius increase with increasing bias on $\Delta\nu$, following the feature seen in the stars flagged for unreliable $\Delta\nu$.
• Figure 5: Distribution of the fractional uncertainty on age from PARAM where $\Delta\nu$ (filled) or $L$ (open) are used as an observational constraint for Kepler (top), K2 (middle) and TESS (bottom). The area under each histogram integrates to one.