\journalname
Astronomy&AstrophysicsReview
Calibrations of M and R.
Fig. \ref{logglogT} highlights the degree of evolution of each star in the sample away from the ZAMS, which is roughly horizontal in this diagram, as a function of temperature (\(\simeq\) spectral type). Evolution without mass loss is generally upwards and to the right in this figure, which suggests that suitable indicators of the degree of evolution of a star are \(T_{\rm eff}\) and \(\log g\), which are observable by both spectroscopic and photometric techniques, together with the metal abundance [Fe/H].