Stellar ages and masses in the solar neighbourhood: Bayesian analysis using spectroscopy and Gaia DR1 parallaxes

Abstract

We present a Bayesian implementation of isochrone fitting in deriving stellar ages and masses, incorporating absolute K magnitude (MK) derived from 2MASS photometry and Gaia DR1 parallax and differentiation between initial bulk metallicity and present-day surface metallicity, with allowance for incorporating further constraints (e.g. asteroseismology) when available. As a test, we re-computed stellar ages and masses of ∼4000 stars in the solar neighbourhood from six well-studied literature samples using both Hipparcos and TGAS parallaxes. Our ages are found to be compatible with literature values but with reduced uncertainties in general. The inclusion of parallax-based MK serves as an additional constraint on the derived quantities, especially when systematic errors in stellar parameters are underestimated. We reconstructed the age–metallicity relationship in the solar neighbourhood by re-analysing the Geneva-Copenhagen Survey with the inclusion of TGAS-parallaxes and initial bulk metallicity sampling. We found a flat trend for disc stars with ages <11 Gyr but with smaller scatter at all ages compared to literature. Show more