Age-dating the young open cluster UBC 1 with g-mode asteroseismology, gyrochronology, and isochrone fitting

Abstract: UBC 1 is an open cluster discovered in Gaia data and located near the edge of the Transiting Exoplanet Survey Satellite's (TESS) continuous viewing zone. We aim to provide age constraints for this poorly studied open cluster from the combination of gravity-mode (g-mode) asteroseismology, gyrochronology, and isochrone fitting. We established the members of UBC 1 from a spatial-kinematic filtering and estimate the cluster age and its parameters. Firstly, we fitted rotating isochrones to the single star cluster sequence. Secondly, using TESS time-series photometry, we explored the variability of the upper main sequence members and identified potential g-mode pulsators. For one star, we found a clear period spacing pattern that we used to deduce the buoyancy travel time, the near-core rotation rate, and an asteroseismic age. For a third independent age estimate, we employed the rotation periods of low-mass members of UBC 1. Based on isochrone fitting, we find $\log t = 8.1\pm0.4$, where the large uncertainty occurs because UBC 1 does not host evolved stars. From asteroseismology of one g-mode pulsator, we find a constrained age of $\log t= 8.24^{+0.43}_{-0.14}$. From gyrochronology based on 17 cool star cluster members, we estimate $\log t = 8.35^{+0.16}_{-0.25}$. Combined, all three methods lead to a consistent age in the range of 150-300 Myr. Our results show that even a single cluster member with identified g modes can improve age-dating of young open clusters. Combining gyrochronology of low-mass members with asteroseismology of intermediate-mass members is a powerful tool for young open cluster modelling, including high-precision age-dating.