Program: GN-2022B-Q-321

The calibration of empirical ages based on rotation, chromospheric emission, and lithium requires data from benchmark star clusters. The large gap in age between the Pleiades (~100 Myr) and Praesepe (~700 Myr) can be filled by previously unappreciated clusters that now have enhanced memberships from Gaia. After measuring rotation periods for dozens of candidates, we found promising color-period distributions for ASCC 41 (300 Myr), Theia 520 (350 Myr), M39 (400 Myr), and NGC 2281 (500 Myr), which now require spectroscopy to complete their thorough characterization. We propose to collect high-resolution spectra with GRACES for each cluster. In summary, we will (1) establish four clusters as new benchmarks for stellar astrophysics using new metallicity data, (2) produce extensive kinematic, rotation, activity, lithium, and other abundance data for a large number of their members, and (3) retune rotation, activity, and Li clocks.