Weakened magnetic braking supported by asteroseismic rotation rates of Kepler dwarfs

TL;DR

This study uses asteroseismic data to confirm that many main sequence stars experience weakened magnetic braking, challenging standard stellar rotation models and providing a large new dataset for future analysis.

Contribution

It presents the largest asteroseismic rotation rate catalogue for main sequence stars and confirms weakened magnetic braking as a common evolutionary phase.

Findings

Weakened magnetic braking is 98.4% more likely in the stellar sample.

Asteroseismic rotation rates can confirm magnetic braking effects across different star activity levels.

The study provides a comprehensive dataset for future stellar rotational evolution research.

Abstract

Studies using asteroseismic ages and rotation rates from star-spot rotation have indicated that standard age-rotation relations may break down roughly half-way through the main sequence lifetime, a phenomenon referred to as weakened magnetic braking. While rotation rates from spots can be difficult to determine for older, less active stars, rotational splitting of asteroseismic oscillation frequencies can provide rotation rates for both active and quiescent stars, and so can confirm whether this effect really takes place on the main sequence. We obtained asteroseismic rotation rates of 91 main sequence stars showing high signal-to-noise modes of oscillation. Using these new rotation rates, along with effective temperatures, metallicities and seismic masses and ages, we built a hierarchical Bayesian mixture model to determine whether the ensemble more closely agreed with a standard rotational evolution scenario, or one where weakened magnetic braking takes place. The weakened magnetic braking scenario was found to be 98.4% more likely for our stellar ensemble, adding to the growing body of evidence for this stage of stellar rotational evolution. This work represents the largest catalogue of seismic rotation on the main sequence to date, opening up possibilities for more detailed ensemble analysis of rotational evolution with Kepler.