The evolution of cool dwarf spin rates: Data, models, and tensions

Marcel Agüeros

Columbia

Stellar ages are notoriously difficult to measure accurately for main-sequence low-mass stars, severely limiting our ability to address questions ranging from the evolutionary state of exoplanets to the chemical history of the Galaxy. Gyrochronology, which uses stellar rotation as a proxy for age, is a promising solution to this quandary. Unfortunately, however, theoretical calibrations of the age-rotation relation have historically been hampered by the lack of rotational measurements for large numbers of low-mass stars with a wide range of well-known ages. We are still far from being able to describe fully the evolution of rotation for low-mass stars, or from being able to use rotation measurements to estimate accurately the ages of isolated field stars. I will first summarize recent ground based and space-based work to characterize the rotational behavior of G, K, and M dwarfs in open clusters ranging in age from 125 Myr (the Pleiades) to 3 Gyr (Ruprecht 147), and then compare these data to each other and to models for stellar spin-down in order to appraise our current understanding of the age-rotation relation.