Atmospheric Parameters and Application of Gaia Color Indices of Main Sequence Stars

Abstract

Using stellar evolution models, empirical atlases of stellar spectra, the ATLAS9 stellar model library, and published relations between observational and astrophysical characteristics of stars of different luminosity classes, we investigate the possibilities of their separation in the space of atmospheric and photometric parameters \(T_{\textrm{eff}}{-}\log g\), \(T_{\textrm{eff}}{-}(B-R)_{0}\) (Johnson), \(T_{\textrm{eff}}{-}(BP-RP)_{0}\) (Gaia). We propose an approximation of the zero age (ZAMS) and terminal age (TAMS) main sequence lines in the \(T_{\textrm{eff}}{-}\log g\) coordinates, and show that more than \(90\%\) of stars of luminosity class III from empirical atlases of stellar spectra are shifted toward smaller values of \(\log g\) relative to TAMS and, as a rule, have values of \(\log g<3.2\). It is shown that the \(T_{\textrm{eff}}{-}(B-R)_{0}\) dependence in the Johnson photometric system is sensitive to the luminosity class in certain ranges of effective temperatures. At the same time, the \(T_{\textrm{eff}}{-}(BP-RP)_{0}\) dependence for main-sequence stars in the Gaia photometric system is found to be valid with an accuracy better than \(0\overset{\textrm{m}}{.}15\) for stars of all luminosity classes and all spectral types earlier than M2.