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

TL;DR

This paper introduces a Bayesian isochrone fitting method that combines spectroscopy and Gaia DR1 parallaxes to derive stellar ages and masses with improved accuracy, applied to solar neighborhood stars.

Contribution

The study develops a Bayesian approach incorporating Gaia parallaxes and metallicity differentiation, reducing uncertainties in stellar age and mass estimates compared to previous methods.

Findings

Ages are consistent with literature but with smaller uncertainties.

Parallax-based absolute magnitude constrains stellar parameters effectively.

Reconstructed age-metallicity relation shows a flat trend for stars younger than 11 Gyr.

Abstract

We present a Bayesian implementation of isochrone fitting in deriving stellar ages and masses, incorporating absolute K magnitude ($\rm M_K$) 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 $\sim 4000$ 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 $\rm M_K$ 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 disk stars with ages $<$11\,Gyr but with smaller scatter at all ages compared to literature.