A Gyrochronology and Microvariability Survey of the Milky Way's Older Stars Using Kepler's Two-Wheels Program

TL;DR

This study explores how Kepler's two-wheel mode can measure stellar rotation periods to improve age estimates of stars, especially beyond 1 billion years, and extend gyrochronology to the full main sequence.

Contribution

It demonstrates the potential of Kepler's two-wheels data to calibrate stellar ages and study magnetic evolution in stars, including M dwarfs and white dwarfs.

Findings

Calibration of rotation-based ages beyond 1 Gyr.

Extension of gyrochronology to fully convective M dwarfs.

Detection of long-period eclipsing binaries and stellar microvariability.

Abstract

Even with the diminished precision possible with only two reaction wheels, the Kepler spacecraft can obtain mmag level, time-resolved photometry of tens of thousands of sources. The presence of such a rich, large data set could be transformative for stellar astronomy. In this white paper, we discuss how rotation periods for a large ensemble of single and binary main- sequence dwarfs can yield a quantitative understanding of the evolution of stellar spin-down over time. This will allow us to calibrate rotation-based ages beyond ~1 Gyr, which is the oldest benchmark that exists today apart from the Sun. Measurement of rotation periods of M dwarfs past the fully-convective boundary will enable extension of gyrochronology to the end of the stellar main-sequence, yielding precise ages ({\sigma} ~10%) for the vast majority of nearby stars. It will also help set constraints on the angular momentum evolution and magnetic field generation in these stars. Our Kepler-based study would be supported by a suite of ongoing and future ground-based observations. Finally, we briefly discuss two ancillary science cases, detection of long-period low-mass eclipsing binaries and microvariability in white dwarfs and hot subdwarf B stars that the Kepler Two-Wheels Program would facilitate.