Monday, June 9 - Plenary Session

Name:  Ruth Angus

Affiliation:  University of Oxford

Title:  Calibrating Gyrochronology using Kepler Asteroseismic targets

Measuring ages for intermediate and low mass stars on the main sequence is challenging, but important for a wide range of studies, from Galactic dynamics to stellar and planetary evolution. The most commonly used dating methods are extremely model dependent and often provide age estimates with uncertainties of order 100% or more. Among the available methods, gyrochronology is a powerful one, because it requires knowledge of only the starís mass (or suitable proxy) and rotation period. However, it is not well calibrated at late ages. The continuous, high precision light curves obtained by Kepler mission are ideally suited to measuring photometric rotation periods and, for a few hundred bright Kepler targets, asteroseismology also provides relatively precise ages. We measured surface rotation periods for 144 Kepler targets with asteroseismic age estimates, which should in principle enable us to test the uniqueness and improve the calibration of the gyrochronology relation at late ages. We use advanced statistical methods to model the relationship between rotation period, age, and mass (or colour or effective temperature) while accounting for measurement uncertainties in all three quantities. Our sample includes both main sequence stars and subgiants, and straddles the Kraft break (only main sequence stars cooler than the Kraft break are expected to follow gyrochronology relations); and this must be taken into account when modelling the data. Once our method is applied to the extended sample of published rotation periods for stars with reliable mass and age estimates, it should enable us to estimate ages for any star with a measured period and mass (or temperature), along with associated uncertainties that reflect both measurement errors and the intrinsic scatter in the gyrochronology relations.