Characterisation of FG-type stars with improved transport of chemical elements

Abstract

Context. The modelling of chemical transport mechanisms is crucial for accurate stellar characterisations. Atomic diffusion is one of these processes and is commonly included in stellar models. However, it is usually neglected for F-type or more massive stars because it produces surface abundance variations that are unrealistic. Additional mechanisms to counteract atomic diffusion must therefore be considered. It has been demonstrated that turbulent mixing can prevent excessive variation in surface abundances, and can also be calibrated to mimic the effects of radiative accelerations on iron. Aims. We aim to evaluate the effect of calibrated turbulent mixing on the characterisation of a sample of F-type stars, and how the estimates compare with those obtained when chemical transport mechanisms are neglected. Methods. We selected stars from two samples: one from the Kepler LEGACY sample and the other from a sample of Kepler planet-hosting stars. We inferred their stellar properties using two grids. The first grid considers atomic diffusion only in models that do not show excessive variation in chemical abundances at the stellar surface. The second grid includes atomic diffusion in all the stellar models and calibrated turbulent mixing to avoid unrealistic surface abundances. Results. Comparing the derived results from the two grids, we find that the results for the more massive stars in our sample show greater dispersion in the inferred values of mass, radius, and age due to the absence of atomic diffusion in one of the grids. This can lead to relative uncertainties for individual stars of up to 5% on masses, 2% on radii, and 20% on ages. Conclusions. This work shows that a proper modelling of the microscopic transport processes is crucial for the accurate estimation of their fundamental properties – not only for G-type stars but also for F-type stars.