Lines of iron as luminosity indicators for F-, G-, K-supergiants

Abstract

We have achieved more than 80 high-precision relations between M_v, T_eff and iron line-depths ratios. These relations have been used for the estimation of the absolute magnitudes M_v for 43 FGK supergiants with an error 0.05^m–0.25^m. The program code based on our relations allows determining absolute magnitudes for supergiants and classical Cepheids of F0–G0 spectral classes and I–II luminosity classes.