\journalname
Astronomy&AstrophysicsReview
However, only for Capella (\(\alpha\) Aur) have the stellar radii been determined from directly measured angular diameters and parallaxes, and even then not yet with the accuracy we require. For the other systems in Table \ref{tableMonly}, radius estimates are based on observed luminosities (from apparent magnitudes and distances) and temperatures. Such estimates are indirect and scale-dependent, and their relative errors – twice those in the temperature – exceed our limit of 3%. Indeed, in several cases the available information on the individual temperatures and luminosities is too fragmentary for any meaningful estimate of individual radii.
Fig. \ref{logRlogMinterf} shows the mass-radius diagram for the interferometric binaries in Table \ref{tableMonly}, with the stars in Table \ref{tableMR} shown as well for comparison. Two salient features appear: The much larger error bars in \(R\) than seen in Fig. \ref{logRlogM}, and the addition of significant numbers of low-mass and evolved stars. The low accuracy of the radii prevents us from including them in the types of discussion contained in the previous sections, but we list them here as a stimulus to observers to complement the excellent mass determinations with the missing essential data of matching quality.
Finally, we note that a fairly large number of single stars exist for which accurate absolute radii have been determined from angular diameters and parallaxes. However, as mass values of matching credentials cannot be determined for these stars, we have decided to not discuss them in the context of this review.