Pushing Gyrochronology to Younger Ages Using Open Clusters

We present stellar rotation period distributions for 7 young open clusters spanning ~10--130 Myr (γ Vel, 25 Ori, NGC 2232, IC 2391, IC 2602, IC 4665 and ABDMG) using TESS photometry. Combining our distributions with those of seven other literature clusters (NGC 2264, NGC 2547, NGC 2541A, α Per, Pleiades, Blanco 1, NGC 2516), yields 14 clusters spanning ~3--150 Myr with which to probe the early evolution of stellar rotation. These rotation distributions show coherent mass-dependent evolutionary trends, first in stellar spin-up followed by spin-down, across the pre-main and early main sequences. These coherent rotational trends suggest that gyrochronology may be applicable to stars younger than the currently accepted lower age anchor of ~80 Myr. However, significant dispersion between stars of a given mass and age exists at these young <80 Myr ages, limiting the power of gyrochronology in isolation. A promising step forward is to combine rotation with additional age-sensitive diagnostics, such as photometric variability amplitude, which exhibits a mass-dependent behaviour that decreases with age. Our current work efforts seek to understand whether the combination of the rotation and photometric variability amplitude can lower the gyrochronal age anchor when combined with other age-sensitive diagnostics.