Distances to Galactic BA supergiants are essential for determining their luminosities, radii, and positions on the Hertzsprung–Russell diagram, yet Gaia parallaxes for these bright, extended sources are often affected by systematics. We compiled a homogeneous sample of 132 B0–A5 supergiants and re-evaluated their distances using a consistent, quality-controlled approach. Parallaxes from Gaia DR3 and EDR3 were corrected for a magnitude–colour zero-point bias and adjusted for excess noise through RUWE-dependent uncertainty inflation. A Bayesian inference with an exponentially decreasing space–density prior was then applied, adopting the catalogue with the smallest penalised total uncertainty. Distances were accepted only when the corrected parallax signal-to-noise ratio exceeded 2.5, the relative uncertainty was below 40%, and key Gaia quality indicators were nominal. The resulting catalogue delivers robust, quality-vetted distances with realistic uncertainties for each star, providing a reliable foundation for deriving fundamental parameters and for future studies of the flux-weighted gravity–luminosity relation and the evolution of Galactic BA supergiants.

Supergiants are luminous post-main-sequence massive stars whose effective temperatures ($T_{\mathrm{eff}}$) are key inputs for stellar evolution and feedback studies. We present a photometry-based procedure to derive $T_{\mathrm{eff}}$ 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 $R_V=A_V/E(B-V)=3.1$. The best-fitting parameters are obtained by minimizing a covariance-weighted ${\chi }^2$ statistic in logarithmic flux space over a grid of $A_V$ 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.

Galactic B- and A-type supergiants serve as critical observational anchors for testing massive-star evolution models and calibrating extragalactic distance indicators. Building upon a uniform $T_{\mathrm{eff}}$ scale established in our previous work, we construct a self-consistent observational Hertzsprung–Russell diagram (HRD) for a homogeneous sample of 84 Galactic BA supergiants to evaluate their fundamental parameters, evolutionary masses, ages, and evolutionary status. Absolute bolometric luminosities are derived by combining Gaia DR3 astrometry with 3D spatial dust reddening maps and theoretical bolometric corrections. Comparison with Geneva evolutionary tracks for solar metallicity ($Z=0.014$), incorporating stellar wind mass loss and rotational mixing, demonstrates that the vast majority of the program stars represent massive post-main-sequence objects with initial masses of approximately 7–$25M_{\odot }$ and ages of $\sim 8$–57 Myr. Our homogeneous analysis also reveals a distinct subgroup of eight low-luminosity objects ($log(L/L_{\odot })<3.5$), including stars whose cataloged luminosity classes are inconsistent with supergiant status as well as objects retaining supergiant spectral classifications despite their unexpectedly low derived luminosities. These findings highlight the importance of combining uniform spectroscopic calibrations with Gaia astrometry to refine Galactic supergiant censuses and improve the empirical basis of the flux-weighted gravity–luminosity relation.