Abstract
Abstract We present empirical effective temperature ( T eff ) calibrations for Galactic supergiants of spectral types B5–A5 based on optical spectra. The relationships were derived from a reference sample with adopted literature temperatures and use equivalent widths, central line depths, and ratios of selected spectral features as temperature indicators. Quadratic relationships are established for individual diagnostics and their ratios. Collectively, the calibrations span a T eff interval from 8400 to 14,700 K, while the validity range of each relationship is individually specified. Detailed quantitative atmospheric analyses remain indispensable for deriving physically consistent stellar parameters. However, their application to extensive spectroscopic samples is observationally and computationally demanding. The empirical relationships presented here provide a homogeneous and readily applicable temperature scale for the characterization of Galactic BA supergiants. The complete calibration tables, including fitted coefficients and uncertainty information, together with an interactive Python tool to apply the relationships, are publicly available through Zenodo. The reduced continuum-normalized spectra and associated metadata are published through a Virtual Observatory–compliant service of the Kazakhstan National Virtual Observatory.