The Kepler field as evidence for metallicity-dependent spin evolution

The spin-down of main sequence cool stars with time can be used as a tool to provide stellar ages under certain conditions. Large photometric surveys such as Kepler, TESS or even GAIA, thus relies on rotation period measurement to estimate the age of cool main sequence stars. Intriguingly, Davenport & Covey (2018) discovered a sequence of cool slower-than-expected rotators in the HR diagram suggesting a deviation from classical gyrochronology from an unknown source. This year, Amard & Matt (2020) and Claytor et al. (2020) showed that metal-rich stars are likely slower rotators on the main sequence due to being cooler and having thicker convective envelope. Using a compilation of mid-to-high resolution spectroscopic surveys of the Kepler field (LAMOST, APOGEE), we are now able to explore the effect of chemical composition on a population of rotating stars. Combined with Kepler and Gaia observations, and a grid of rotating stellar evolution model over a large range of mass and metallicity, this new sample allows us to reproduce the feature noticed by Davenport & Covey (2018) and to a later extent to explore and constrain the link between chemical composition, mass, rotation and activity