Functional relationships for Teff and log g in F-G supergiants from uvby - β photometry

Abstract

From photoelectric uvby − β data and recent accurate synthetic and spectroscopic values of Teff and log g for 50 F-G supergiants, we have calculated functional relationships that lead to initial estimates of effective temperature and gravities for these types of stars. It is shown that while the Teff relationships are calculated using the data on young massive supergiants, they are also valid for evolved stars of similar temperatures like post-AGB and RV Tau stars. The gravity can also be predicted from the Δ[c1] index with an uncertainty of about 0.26 dex. Although a clear and significant trend between MV and Δ[c1] is seen, no calibration is found that predicts accurate values of MV.