An asteroseismic age estimate for the Pleiades using a neural-network emulator of rotating δ Scuti pulsation models
Anuj Gautam, Simon J. Murphy
Abstract
Asteroseismology of δ Sct stars has strong potential for determining the ages of young stars through individual mode fitting. We present a neural-network emulator trained on approximately 46 million rotating pulsation models. From stellar mass, metallicity, age, and equatorial rotation velocity, it predicts 12 classical observables, two asteroseismic scalars, and the p mode, f mode and low-order g mode frequencies for degrees ℓ=0-3, including the individual m components of rotationally split multiplets. We couple the emulator to nested sampling through a multivariate likelihood that propagates correlated emulator residuals, making full Bayesian posterior exploration practical. Applied to five δ Sct stars in the Pleiades observed by TESS, the framework gives mutually consistent individual asteroseismic ages of 107-117 Myr. Combining their age posteriors gives a cluster age of 113.3±4.5 Myr (statistical), consistent with the 112±5 Myr lithium-depletion-boundary age and the 110-160 Myr range from rotating-isochrone fitting. Together with spectroscopic vsini, the inferred equatorial velocities also provide post-fit inclination estimates. Separate perturbed-grid tests using 100 matched synthetic pairs per input-physics variation give median absolute age shifts of 2.1, 2.3, and 5.2 Myr for |Δf_ov|=0.005, |Δα_MLT|=0.1, and |ΔY|=0.02, respectively; the corresponding 90th percentile shifts are 6.5, 7.6, and 16.2 Myr. These tests describe conditional population sensitivities, not a systematic uncertainty on the Pleiades age. Together, the cluster-age agreement and the scale of these input-physics sensitivities support δ Sct asteroseismology as a complementary age estimation method for young stars.