Observations of 48 red-clump stars were obtained in the H band with the PIONIER instrument installed at the Very Large Telescope Interferometer. Limb-darkened angular diameters were measured by fitting radial intensity profile I(r) to square visibility measurements. Half the angular diameters determined have formal errors better than 1.2%, while the overall accuracy is better than 2.7%. Average stellar atmospheric parameters (effective temperatures, metallicities and surface gravities) were determined from new spectroscopic observations and literature data and combined with precise Gaia parallaxes to derive a set of fundamental stellar properties. These intrinsic parameters were then fitted to existing isochrone models to infer masses and ages of the stars. The added value from interferometry imposes a better and independent constraint on the R-Teff plane. Our derived values are consistent with previous works, although there is a strong scatter in age between various models. This shows that atmospheric parameters, mainly metallicities and surface gravities, still suffer from a non-accurate determination, limiting constraints on input physics and parameters of stellar evolution models.
@article{arxiv.1806.09572,
title = {Fundamental properties of red-clump stars from long-baseline H-band interferometry},
author = {A. Gallenne and G. Pietrzyński and D. Graczyk and N. Nardetto and A. Mérand and P. Kervella and W. Gieren and S. Villanova and R. E. Mennickent and B. Pilecki},
journal= {arXiv preprint arXiv:1806.09572},
year = {2018}
}