Exploring the Evolution of Stellar Rotation Using Galactic Kinematics

• Published in: The Astronomical journal Vol. 160; no. 2; pp. 90 - 100
• Main Authors: Angus, Ruth, Beane, Angus, Price-Whelan, Adrian M., Newton, Elisabeth, Curtis, Jason L., Berger, Travis, van Saders, Jennifer, Kiman, Rocio, Foreman-Mackey, Daniel, Lu, Yuxi (Lucy), Anderson, Lauren, Faherty, Jacqueline K.
• Format: Journal Article
• Language: English
• Published: Madison The American Astronomical Society 01.08.2020; IOP Publishing
• Subjects: Angular momentum; Angular momentum transport; Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Clusters; DISPERSIONS; DWARF STARS; Galactic evolution; Galactic rotation; Kinematics; Late-type stars; Low mass stars; MAIN SEQUENCE STARS; MASS; Massive stars; Milky Way disk; Milky Way dynamics; Momentum transport; ROTATION; Solar analogs; STAR EVOLUTION; Stellar activity; Stellar age; Stellar evolution; Stellar kinematics; Stellar magnetic fields; Stellar phenomena; Stellar rotation; TEMPERATURE DEPENDENCE; TIME DEPENDENCE
• ISSN: 0004-6256; 1538-3881; 1538-3881
• DOI: 10.3847/1538-3881/ab91b2

The rotational evolution of cool dwarfs is poorly constrained after ∼1-2 Gyr due to a lack of precise ages and rotation periods for old main-sequence stars. In this work, we use velocity dispersion as an age proxy to reveal the temperature-dependent rotational evolution of low-mass Kepler dwarfs and demonstrate that kinematic ages could be a useful tool for calibrating gyrochronology in the future. We find that a linear gyrochronology model, calibrated to fit the period- relationship of the Praesepe cluster, does not apply to stars older than around 1 Gyr. Although late K dwarfs spin more slowly than early-K dwarfs when they are young, at old ages, we find that late K dwarfs rotate at the same rate or faster than early-K dwarfs of the same age. This result agrees qualitatively with semiempirical models that vary the rate of surface-to-core angular momentum transport as a function of time and mass. It also aligns with recent observations of stars in the NGC 6811 cluster, which indicate that the surface rotation rates of K dwarfs go through an epoch of inhibited evolution. We find that the oldest Kepler stars with measured rotation periods are late K and early M dwarfs, indicating that these stars maintain spotted surfaces and stay magnetically active longer than more massive stars. Finally, based on their kinematics, we confirm that many rapidly rotating GKM dwarfs are likely to be synchronized binaries.