Asteroseismic masses, ages, and core properties of gamma Doradus stars using gravito-inertial dipole modes and spectroscopy

Abstract

The asteroseismic modelling of period spacing patterns from gravito-inertial modes in stars with a convective core is a high-dimensional problem. We utilize the measured period spacing pattern of prograde dipole gravity modes (acquiring Pi(0)), in combination with the effective temperature (Teff) and surface gravity (log g) derived from spectroscopy, to estimate the fundamental stellar parameters and core properties of 37 gamma Doradus (gamma Dor) stars whose rotation frequency has been derived from Kepler photometry. We use two 6D grids of stellar models, one with step core overshooting and another with exponential core overshooting, to evaluate correlations between the three observables Pi(0), T-eff, and log g and the mass, age, core overshooting, metallicity, initial hydrogen mass fraction, and envelope mixing. We provide multivariate linear model recipes relating the stellar parameters to be estimated to the three observables (Pi(0), T-eff, log g). We estimate the (core) mass, age, core overshooting, and metallicity of gamma Dor stars from an ensemble analysis and achieve relative uncertainties of similar to 10 per cent for the parameters. The asteroseismic age determination allows us to conclude that efficient angular momentum transport occurs already early on during the main sequence. We find that the nine stars with observed Rossby modes occur across almost the entire main-sequence phase, except close to core-hydrogen exhaustion. Future improvements of our work will come from the inclusion of more types of detected modes per star, larger samples, and modelling of individual mode frequencies.