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.

Comparison of the spectra obtained at different observing dates shows significant variations in the complex Hα and Hβ line profiles, such as a systematic increase in their emission peak strengths in 2025÷2026 compared to those observed in 2013 as well as a strong variability in their wind component. A detected variable radial velocity V_⊙ from -20 to -68 km/s with a standard deviation of the mean value of K∼8.0 km/s can be interpreted as a result of pulsations or the presence of a companion. The stationary positions of forbidden lines with a mean radial velocity of V_⊙=-51.38±0.26 km/s are taken as an improved systemic velocity. Overall, a set of properties of IRAS 01005+7910 points to its status as a post-AGB star, which has undergone the hot-bottom burning phase.

We present new results of the investigation of the optical spectrum features of the central star with the B[e] phenomenon in the system of the IR-source IRAS 01005+7910 using high-resolution (R≥ 60,000) spectroscopy data taken by the 6 m BTA telescope with the NES spectrograph. Comparison of the spectra obtained at different times shows significant variations in the complex Hα and Hβ line profiles, such as a systematic increase in their emission peak strengths in 2025–2026 compared to those observed in 2013 as well as a strong variability in their wind component. A detected variable radial velocity V⊙ from −20 to −68 km s−1 with a standard deviation of the mean value of K = 8.0 km s−1 can be interpreted as a result of pulsations or the presence of a companion. The stationary positions of forbidden lines with a mean radial velocity of V⊙=−51.38±0.26 km s−1 are taken as an improved systemic velocity. Overall, a set of properties of IRAS 01005+7910 points to its status as a post-AGB star, which has undergone the hot-bottom burning phase.

The atlas of the spectrum of the B[e] star CI Cam obtained with the 6-m BTA telescope of the SAO RAS applying the NES spectrograph in the wavelength range of 395–780 nm with a resolution of λ/Δλ≥ 60 000 is presented. The atlas identifies about 400 spectral features and illustrates the diversity of spectral features of the unique star, forming in a complex circumstellar environment. The spectrum is dominated by forceful single-peaked H I, He I emissions and numerous double-peaked permitted and forbidden emission lines of ions of chemical elements starting from the CNO triad up to metals (Mg, Al, Ti, V, Cr, Fe) with ‘‘rectangular’’ profiles. The Fe II and [Fe II] emissions predominate in the spectrum. However, several double-peaked forbidden ion emissions were also detected: [V II], [Cr II], [Ni II]. The atlas is presented graphically, with a separate figure corresponding to each échelle order. A list of identified lines, including a number of known interstellar features is presented in table form. The supergiant status of CI Cam is confirmed by the richness of its spectrum with different features of nitrogen.

We present a detailed analysis of the early post-mass-transfer binary system HD 698 (V742 Cas), combining high-resolution optical spectroscopy, long-baseline interferometry, and radiative transfer modeling. Counter-phased RV curves reveal a circular orbit with a period of 55.927 +/- 0.001 d and component masses of MBe = 7.48 +/- 0.07 M circle dot and Mcomp = 1.23 +/- 0.02 M circle dot. The Be primary is traced via broad H alpha wings, while narrow metallic absorption lines originate from a slowly rotating companion. The angular separation measured via interferometry implies a dynamical distance of 888 +/- 5 pc. The spectral energy distribution is best reproduced with a color excess E(B - V) = 0.321 +/- 0.016 due to interstellar reddening and a moderately dense viscous decretion disk with base density rho 0 similar or equal to 5 x 10-12 g cm-3 at r = Req, declining radially as rho(r) proportional to r-n with n = 3.0. The companion is found to be a luminous and inflated star with Teff,comp=10.0-0.1+0.2 kK, Rcomp=13.1-0.2+0.2R circle dot , and logL/L circle dot=3.19 , contributing significantly to the flux (Lcomp/LBe similar to 0.3). Spectral line mismatches provide further circumstantial evidence that the companion is hydrogen poor, consistent with a stripped-envelope star enriched by CNO processing. HD 698 thus belongs to the emerging class of Be + bloated O/B binaries, representing a short-lived, high-luminosity post-mass-transfer phase, when the stripped donor is still spectroscopically detectable before reaching the subdwarf phase.

The B[e] phenomenon discovered nearly 50 years ago features the presence of forbidden emission lines due to extended and dense circumstellar gas and large IR excesses due to the radiation from circumstellar dust in a wide variety of objects from pre-main-sequence stars to Planetary Nebulae. It also shows up in a small group of supergiants that includes Luminous Blue Variables, such as η Carinae. Over the years, some of them were proven to be binary systems, but the presence of a secondary component in other is still elusive. At the same time, there is growing evidence that the B[e] phenomenon can be due to binary mergers or interactions in triple systems.

We present new spectroscopic orbits for the bright binaries Mizar B, 3 Pup, ν Gem, 2 Lac, and ϕ Aql. Our analysis is based on medium-resolution (R≈ 12,000) échelle spectra obtained with the 0.81-m telescope and fiber-fed eShel spectrograph of the Three College Observatory (Greensboro, NC, USA) between 2015 and 2024. Orbital elements were inferred with an affine-invariant Markov-chain Monte-Carlo sampler; convergence was verified through the integrated autocorrelation time and the Gelman–Rubin statistic. Errors quote the 16th–84th-percentile credible intervals. Compared with previously published orbital solutions for the studied stars, our method improves the root-mean-square residuals by 25–50% and bring the 1σ uncertainties on the radial velocity (RV) semi-amplitudes down to 0.02–0.15 km s−1. These gains translate into markedly tighter mass functions and systemic RVs, providing a robust dynamical baseline for future interferometric and photometric studies. A complete Python analysis pipeline is openly available in a GitHub repository, ensuring full reproducibility. The results demonstrate that a Bayesian RV analysis with well-motivated priors and rigorous convergence checks yields orbital parameters that are both more precise and more reproducible than previous determinations, while offering fully transparent uncertainty budgets.

AS 314 (V452 Sct) is a poorly studied early-type emission-line star, which exhibits an infrared excess at wavelengths longer than 10 μm. Its earlier studies have been limited to small amounts of observational data and led to controversial conclusions about its fundamental parameters and evolutionary status. Comparison of high-resolution spectra of AS 314 taken over 20 years ago with those of Luminous Blue Variables and other high-luminosity objects suggested its observed properties can be explained by a strong stellar wind from a distant (D∼10 kpc) massive star, possibly in a binary system. However, a recent assessment of its low-resolution spectrum along with a new distance from a Gaia parallax (∼1.6 kpc) resulted in an alternative hypothesis that AS 314 is a low-mass post-asymptotic giant branch (post-AGB) star. The latter hypothesis ignored the high-resolution data, which gave rise to the former explanation. We collected over 30 mostly high-resolution spectra taken in 1997–2023, supplemented them with results of long-term photometric surveys, compared the spectra and the spectral energy distribution with those of post-AGB objects and B/A supergiants, and concluded that the observed properties AS 314 are more consistent with those of the latter.

MWC 342 (V1972 Cyg) was discovered nearly 90 years ago as an early-type emission-line star. It was among the first hot stars whose strong infrared excess was detected in the early 1970s. Several mostly short-term photometric and spectroscopic studies resulted in contradictory conclusions about the nature and evolutionary status of MWC 342. It has been classified as a pre-main-sequence Herbig Be star, an evolved suspected binary system, and a long-period variable star. Suggestions on the nature of the secondary component to this B0/B1 primary included a cool M-type giant and an X-ray source. We collected medium- and high-resolution optical spectra of MWC 342 taken in 1994–2024 as well as optical photometric data taken in 1986–2024. Analysis of these data shows strong variations in the object’s brightness and spectral line properties at various time scales, but no strictly periodic phenomena have been found. Inparticular, such a long-term dataset allowed us to reveal the optical brightness variations over a nearly 20-year-long quasi-period, as well as their anti-correlation with the Hα emission-line strength. Also, we did not confirm the presence of He ii emission lines and absorption lines of the star’s atmosphere that were suspected in previously published studies.

In this study, we present refined orbital and fundamental parameters of the Galactic B[e] supergiant binary system HD 327083 using the Bayesian Markov Chain Monte Carlo (MCMC) method applied to the radial velocities data of HD 327083. We found that the system is well described by a circular orbital model with the mass ratio of the components of q=1.15±0.07. We modeled the evolutionary history of the system using MESA code. Initially, the system was formed by a binary with the orbital period of Porb=108 day, which contained stars with 13.00 ±0.05 M⊙ and 11.50±0.05 M⊙ masses. They had a relatively slow rotation υrot=0.40±0.13υcrit and provided a strong stellar wind. The current system age is 13.6±0.1 Myr, and the state of the system corresponds to a close filling of the high massive component’s Roche lobe and a beginning of the mass transfer. The mass-transfer event will occur in a short interval of ≲0.1 Myr only. After that, the mass of the post-primary drops to ≈5 M⊙, the post-secondary mass grows until ≈20 M⊙, and the binary will convert to a detached system with a long orbital period of ≈700 days.

Objects with the B[e] phenomenon, whose defining features are the presence of forbidden emission lines and infrared excess coming from circumstellar dust, represent a broad range of evolutionary stages from pre-main-sequence to planetary nebulae. They are important for understanding mechanisms of the circumstellar matter formation and evolution. However, it is not easy to discover them, especially among faint stars, as forbidden emission lines are usually weak and hardly noticeable in low-resolution spectra. We developed photometric criteria to search for candidate objects with this phenomenon based on a combination of optical and near-infrared color indices and found nearly 40 objects that satisfy these criteria. Spectroscopy of the candidates allows us to make more confident conclusions on their classification. We present the results of our photometric and spectroscopic observations of six objects, which are part of a large list of ∼40 objects that satisfy our photometric selection criteria for candidate objects with the B[e] phenomenon. Forbidden lines of neutral oxygen were clearly detected in the optical spectrum of one object (VES 683) and suspected in three others. One object, AS 415, is most likely a binary system with components that exhibit partial eclipses but without the B[e] phenomenon, while IRAS 20402 + 4638 may be a luminous member of the FS CMa objects group.

We present a detailed spectrophotometric study of nova LMCN 2009-05a, located in the Large Magellanic Cloud (LMC). Photometric observations reveal a dust dip in the optical light curve, classifying it as a D-class nova. Light curve analysis yields t _2 and t _3 decline times of approximately 46 and 80 days, respectively, placing the nova in the category of moderately fast novae. Spectroscopic observations cover multiple phases, including pre-maximum, early decline, and nebular. The spectra are initially dominated by hydrogen Balmer and Fe II lines with P-Cygni profiles, which later transition into pure emission. During the optical minimum, a discrete absorption feature was observed in the H α and [O I ] line profiles. The physical and chemical properties during the early decline and nebular phases were analyzed using the photoionization code CLOUDY. Dust temperature, mass, and grain size were estimated through spectral energy distribution fitting to the WISE data. On day 395 post-outburst, we estimate the dust temperature to be approximately 700 K. Additionally, we examined the correlation between dust condensation time ( t _cond ) and t _2 for LMC novae, finding a trend consistent with previous studies of Galactic novae.

HD 50138 is a 6.6 mag emission-line B–type star, whose nature is still controversial. It has been thought to be a pre-main-sequence Herbig Be star and an evolved object with the B[e] phenomenon, possibly a mass-transferring binary system. However, it has mostly been studied on short timescales. We collected ∼1000 medium- and high-resolution spectra and available optical photometric data, which cover a time frame from 1981 to 2025, and extended the study from emission lines to a range of absorption lines. A few episodes of dramatic emission-line strength variations were uncovered as well as fast variations of the absorption line widths on timescales of several days. We also found a few previously unreported fadings of the star’s optical brightness seemingly associated with the Hα line profile changes. At the same time, it is still unclear whether the object is a single star or a binary system, as no regular variations of its observed parameters have been detected.

We present a Doppler tomography study of the Be star HD 698, recently resolved via interferometry as a post-mass-transfer binary system consisting of a Be star and a stripped, pre-subdwarf companion. Based on 76 high-resolution optical spectra obtained between 2014 and 2023, we analyze the Hα and Hβ emission lines and apply Doppler tomography to map the structure of the circumstellar disk. The Hα line reveals an asymmetric, multi-component velocity distribution, with an emission feature closely following the orbital motion of the companion. V/R variations in both Hα and Hβ lines are phase-locked with the companion’s orbital motion, indicating a tidally induced disk asymmetry. We discuss possible origins of the companion-centered Hα emission, including a circumsecondary disk, a transient mass-transfer stream, and stellar wind.

Based on 583 radial velocity (RV) measurements we obtained at the Three College Observatory (TCO, North Carolina, USA) in 2015–2024, (including 396 not previously analyzed from 2020–2024) as well as on 236 RV data from the German amateur R. Bücke (2011–2022), we calculated the pulsation period and amplitude of the Cepheid Polaris Aa system (α UMi). The analysis showed that the pulsation period was stable within a few minutes in 2020–2024. During this time, the pulsation amplitude was increasing and reached the 1960s level (4–6 km s−1), when its sharp decline began. Since its new growth began after Polaris Ab, the system secondary component, passed a periastron, we concluded that the observed amplitude changes were due to its orbital motion. It is clear that Polaris Aa is returning to normal pulsating activity.

Results are reviewed of a long-term program of binary systems observing since 2013 at the 0.81 m telescope of the Three College Observatory in North Carolina, USA, with an e ' chelle spectrograph at a medium spectral resolution. The target list includes recognized and suspected binary systems with normal stars (no spectral lines in emission), classical Be stars, and objects with the B[e] phenomenon. The results include refinement of the orbital elements of bright binaries previously observed with photographic plates, further evidence for phased -locked peak intensity variations of double -peaked line profiles in Be binaries, and recent discoveries of binaries among objects with the B[e] phenomenon.

High-resolution optical spectra of the B[e] star CI Cam were obtained on arbitrary dates 2002–2023 using the 6-meter BTA telescope with the echelle spectrograph NES. The variability over time of the powerful emissions of Hα and He I profiles is found. For two-peak emissions with “rectangular” profiles, the intensity ratio of blue-shifted and red-shifted peaks is V/R⩾ 1 , except one date. A decrease in the intensity of all double-peaked emissions with “rectangular” profiles was revealed as they moved away in time from the 1998 outburst. The average radial velocity for emissions of this type for all observation dates varies in the range V_r(emis- d) = - (50.8 ÷ 55.7) ± 0.2 km/s. The half-amplitude of the change (standard deviation) is equal to ΔV_r = 2.5 km/s. The velocity for single-peaked ion emissions (Si III, Al III, Fe III) differs little from the values of V_r(emis- d) , but the measurement accuracy for these emissions is worse: the average error for different dates ranges from 0.4 to 1.3 km/s. The systemic velocity is assumed to be V_sys = - 55.4 ± 0.6 km/s according to the stable position of the forbidden emission [N II] 5755 Å. The position of single-peak emissions [O III] 4959 and 5007 Å is also stable: V_r([O III]) = - 54.2 ± 0.4 km/s. Emissions [O I] 5577, 6300, 6363 Å, [Ca II] 7291 and 7324 Å are absent from the spectra. Appearance of the emission near 4686 Å is an infrequent event, its intensity rarely exceeds the noise level. Only a wide asymmetric emission with an intensity of about 16

κ Draconis is a binary system with a classical Be star as the primary component. Its emission-line spectrum consists of hydrogen lines, notably the Hα line with peak intensity ratio (V/R) variations phase-locked with the orbital period P = 61.55 days. Among binaries demonstrating the Be phenomenon, κ Dra stands out as one of a few systems with a discernible mass of its secondary component. Based on more than 200 spectra obtained in 2014–2023, we verified the physical parameters and constructed the mass function. We used part of these data obtained in 2014–2021 to investigate regions in the circumstellar disk of the primary component that emit the Hα line using the Doppler tomography method. The results show that the disk has a non-uniform density distribution with a prominent enhancement at Vy ≈ 99 km s−1 and Vx≈−6 km s−1 that corresponds to a cloud-like source of the double-peaked Hα line profile. We argue that this enhancement’s motion is responsible for the periodic variations in the Hα V/R ratio, which is synchronised in orbital phase with the radial velocity (RV) of absorption lines from the atmosphere of the primary component.

HD 327083 is a binary system that consists of two supergiant components and exhibits the B[e] phenomenon. In this paper, we report the determination of a new set of the system's fundamental parameters using a combination of photometric and spectroscopic data as well as the Gaia EDR3 distance. We found that the orbital period of the system is 107.68 +/- 0.02 days. The spectral line content implies the effective temperatures of approximate to 7000 K and 25,400 +/- 1400 K, while the photometric variations are consistent with the radii of approximate to 106 R circle dot and approximate to 10 R circle dot for the cool and hot components, respectively. The absorption lines of the cool component show a radial velocity semiamplitude of 48.3 +/- 1.7 km s-1, similar to that of the emission lines that originate around the hot component. The inclination of the system to the line of sight is 47 - 20 + 17 degrees. Modeling of the system's evolutionary history suggests that the components have masses of similar to 12.5 M circle dot and currently undergo mass transfer between them. This configuration, which takes in heating of the surface of the cool component by the radiation from the hot one, can reproduce the photometric and spectroscopic data and is in agreement with previous infrared observations of the circumbinary disk. The results of this study further confirm the hypothesis that the reason for the presence of the B[e] phenomenon in most objects is a consequence of the evolution of various binary systems.