Exploring the Evolution of Stellar Rotation Using Galactic Kinematics

Abstract

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.

WASP-107b’s Density Is Even Lower: A Case Study for the Physics of Planetary Gas Envelope Accretion and Orbital Migration

“…We also use kinematic ages of Kepler field stars to calibrate the model for old K and early M dwarfs, where there is a dearth of suitable open cluster calibration stars. These kinematic ages also reflect the stalled magnetic braking behavior seen in open clusters (Angus et al 2020).…”

Detections of solar-like oscillations in dwarfs and subgiants with Kepler DR25 short-cadence data

“…In order to learn about the magnetic activity of stars with photometric data, we can use rotational modulation that results from the presence of active regions on the stellar surface. Additionally, the study of stellar rotation can provide key information for the understanding of angular momentum transport (e.g., Aerts et al 2019;van Saders et al 2019;Angus et al 2020;Curtis et al 2020;See et al 2021). Several studies have been carried out on the basis of Kepler and K2 data to measure surface rotation periods in a large sample of stars (e.g.m McQuillan et al 2014;Santos et al 2019;Reinhold & Hekker 2020;Gordon et al 2021;Santos et al 2021); furthermore, combined with the precise ages of stars, such as those obtained with asteroseismology or for clusters, it is possible to improve the general understanding of rotation-age relationships (e.g., Barnes 2003;Mamajek & Hillenbrand 2008;Angus et al 2015;van Saders et al 2016;Hall et al 2021;Godoy-Rivera et al 2021).…”

TOI-1259Ab – a gas giant planet with 2.7 per cent deep transits and a bound white dwarf companion

“…We also used kinematic ages of Kepler field stars to calibrate this model for old K and early M dwarfs, where there is a dearth of suitable open cluster calibration stars. These kinematic ages also reflect the stalled magnetic braking behaviour seen in open clusters (Angus et al 2020).…”

“…When estimating the ages of K dwarfs using gyrochronology, it is essential to account for 'stalled magnetic braking'. Recent observations have revealed that rotational evolution is inhibited for middle-aged K dwarfs (Curtis et al 2019;Angus et al 2020). This stalled rotational evolution is thought to be caused by an internal redistribution of angular momentum (Spada & Lanzafame 2020).…”