Abstract
Supergiants are luminous post-main-sequence massive stars whose effective temperatures (Teff) are key inputs for stellar evolution and feedback studies. We present a photometry-based procedure to derive Teff for a sample of galactic supergiants of spectral types B and A by fitting the spectral energy distributions (SEDs) in the UV-to-mid-IR range to ATLAS9 model spectra converted into synthetic photometry using the corresponding passband transmission profiles while simultaneously solving for the line-of-sight extinction. The SEDs were constructed from published data taken in different photometric systems (Johnson or Kron–Cousins UBVRI, Strömgren uvby, JHK magnitudes from various sources, and AllWISE) and supplemented with UV TD-1 fluxes for brighter stars. The interstellar extinction law is based on Cardelli, Clayton & Mathis approximation assuming a total-to-selective ratio RV=AV/E(B−V)=3.1. The best-fitting parameters are obtained by minimizing a covariance-weighted χ2 statistic in logarithmic flux space over a grid of AV values and a discrete model grid. We test the method on 20 targets and find generally good agreement with published literature temperature estimates. The main limitations are non-simultaneous photometry for possibly variable objects and the residual coupling between temperature and reddening in broadband SED fitting. This study is intended as a methodological demonstration on a pilot sample rather than a definitive parameter catalog.