Metallicity and absolute magnitude calibrations for F-G type main-sequence stars in the Gaia era

In this study, photometric metallicity and absolute magnitude calibrations were derived using F-G spectral type main-sequence stars in the Solar neighbourhood with precise spectroscopic, photometric and Gaia astrometric data for UBV photometry. The sample consists of 504 main-sequence stars covering the temperature, surface gravity and colour index intervals 5300< T_eff < 7300 K, log g > 4 (cgs) and 0.3<(B-V)_0<0.8 mag, respectively. Stars with relative trigonometric parallax errors σ _π/π≤ 0.01 were preferred from Gaia DR2 data for the estimation of their M_V absolute magnitudes. In order to obtain calibrations, (U-B)_0 and (B-V)_0 colour indices of stars were preferred and a multi-variable second order equation was used. Calibrations are valid for main-sequence stars in the metallicity and absolute magnitude ranges -2<[/]<0.5 dex and 2.5< M_V<6 mag, respectively. The mean value and standard deviation of the differences between original and estimated values for the metal abundance and absolute magnitude are ⟨Δ[/]⟩ =0.00± 0.11 dex and ⟨Δ M_V⟩ =0.00± 0.22 mag, respectively. In this work, it has been shown that more precise iron abundance and absolute magnitude values were obtained with the new calibrations, compared to previous calibrations in the literature.