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.

We present MERLIS , a Python-based pipeline for the automated measurement of stellar spectral-line parameters in medium-resolution spectra. The framework provides a unified approach to determining equivalent width, line depth, and full width at half-maximum for both narrow metallic lines and broad Balmer features, enabling homogeneous analysis across line profiles of substantially different morphology. The method combines local continuum renormalization, multimodel analytic profile fitting, adaptive determination of line-integration boundaries, and Monte Carlo uncertainty estimation. Broad hydrogen lines are treated using a dedicated fitting strategy designed to account for their extended wings and core-wing structure, while narrower features are analyzed through automated model selection among several candidate profile families. For multiepoch datasets, the pipeline also incorporates radial velocity consistency checks and weighted spectrum combination to reduce profile smearing and improve the robustness of the final measurements. We describe the methodology and validate its performance using both synthetic and observed stellar spectra. The workflow is further applied to 137 individual spectra of Galactic BA-type supergiants, producing a homogeneous catalog of line-profile measurements for subsequent temperature-sensitive spectroscopic analyses. The pipeline delivers reproducible line measurements, homogeneous uncertainty estimates, and fit-quality diagnostics suitable for precision studies of spectral-line variability in stellar spectroscopy.

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.

LN Hya (BS 4912; HD 112374) has long been regarded as a post-AGB F-type supergiant, located at a high Galactic latitude (b = +36°.3). Earlier studies relied on limited spectroscopic and photometric material. We present a new data set comprising 73 medium-resolution (R ≈ 12,000) optical spectra obtained at the 0.81-meter telescope of the Three College Observatory (North Carolina, USA) in 2021—2025. We found regular variations in the radial velocities (RV) of absorption lines with a period of 148.63 ± 0.09 days. Our observations cover 10 most recent variability cycles and suggest that LN Hya is a binary system with an eccentric orbit (e = 0.19±0.02). In this paper, we describe the data reduction and analysis process as well as some spectral features of the system. Future plans for a deeper study of LN Hya that include analyzing existing photometric data and correlating them with the spectral variability are outlined.зорі над асимптотичною гілкою гігантів

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.