Gyrochronological dating of the stellar moving group Group X

TL;DR

This paper uses gyrochronology and other methods to determine the age of the stellar moving group Group X as approximately 300 million years, refining its characterization and ruling out previous associations.

Contribution

It provides the first gyrochronological age estimate for Group X using TESS data, combining multiple methods for a robust age determination.

Findings

Gyro age of Group X is approximately 300 Myr.

The age estimate rules out connection with the older Coma Berenices cluster.

Consistent age estimates from isochrone fitting and individual star analysis.

Abstract

Gyrochronology is one of the methods currently used to estimate the age of stellar open clusters. Hundreds of new clusters, associations, and moving groups unveiled by Gaia and complemented by accurate rotation period measurements provided by recent space missions such as Kepler and TESS are allowing us to significantly improve the reliability of this method. We use gyrochronology, that is, the calibrated age-mass-rotation relation valid for low-mass stars, to measure the age of the recently discovered moving group Group X. We extracted the light curves of all candidate members from the TESS full frame images and measured their rotation periods using different period search methods. We measured the rotation period of 168 of a total of 218 stars and compared their period-colour distribution with those of two age-benchmark clusters, the Pleiades (125 Myr) and Praesepe (625 Myr), as well as with the recently characterised open cluster NGC3532 (300 Myr). As result of our analysis, we derived a gyro age of 300$\pm$60 Myr. We also applied as independent methods the fitting of the entire isochrone and of the three brightest candidate members individually with the most precise stellar parameters, deriving comparable values of 250 Myr and 290 Myr, respectively. Our dating of Group X allows us to definitively rule out the previously proposed connection with the nearby but much older Coma Berenices cluster.