Positional and kinematic parameters of hypergiants HD 168607 B8.5 Ia-0, HD 168625 B5.0 Ia-0, Schulte 12 B4.0 Ia-0, and 6 Cas AA2.5 Ia-0 belonging to OB associations do not indicate that they are ejected from their formation regions in molecular clouds, and the field hypergiant HD 183143 B7 Ia-0 located in the gap between spiral arms does not show anomalously high velocity relative to the stellar and gas neighborhood. We give two examples of the refinement of the distance to stars from the interstellar line profiles in their spectra.

The first high-resolution spectra (resolving powers of R ≥ 60 000) of the emission-line star VES 723, which has an unknown evolutionary status, were taken at the 6-m Big Telescope Alt-Azimuthal and the 3.6-m Canada–France–Hawaii Telescope. The spectrum is dominated with powerful emission lines of neutral hydrogen and helium, and forbidden singly ionized nitrogen. The Hα and He i lines were found to exhibit broad foundations of the emission profiles at least 250 km s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> wide. The strongest emission lines exhibit no noticeable variations during the observing period (2011–2017) except for the He i lines. The spectra contain multicomponent interstellar absorptions of Na i and K i (mult. 1) and several strongest diffuse interstellar bands, while photospheric absorptions have not been detected. The average radial velocity of the forbidden [N ii] emission line centres was adopted as the systemic velocity (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sys</inf> ≈ −52 km s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> ), which indicates a large distance of ≈6 kpc. Our luminosity estimates of log  L/L <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">⊙</inf> = 3.7−4.0 for two different Gaia distance measurements, along with an effective temperature of T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</inf> = 25 000 ± 2000 K and a fast decrease of the infrared flux longward of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda \sim 10\, \mu{\rm m}$</tex> , allow us to suggest that VES 723 is neither a pre-main-sequence Herbig B[e] star nor a B[e] supergiant but rather a member of the FS CMa group of objects with the B[e] phenomenon.

Using the data from the second release of the Gaia exoatmospheric astrometric observatory archive the structure of the Cas5 OB association and the parameters of stars of extremely high luminosity that it contains have been refined. Two groups of OB stars have been isolated in the direction of the association at distances 3.3 and 4.3 kpc.

We report the results of long-term spectroscopic monitoring of the A-type supergiant with the B [e] phenomenon 3 Pup = HD 62623. We confirm earlier findings that it is a binary system. The orbital parameters were derived using cross-correlation of the spectra in a range of 4460-4632 angstrom, which contains over 30 absorption lines. The orbit was found to be circular with a period of 137.4 +/- 0.1 days, radial velocity semiamplitude K-1 = 5.0 +/- 0.8 km s(-1), systemic radial velocity gamma = +26.4 +/- 2.0 km s(-1), and mass function f (m) = (1.81(-0.76)(+0.97)) x 10(-3) M-circle dot. The object may have evolved from a pair with initial masses of similar to 6.0 M-circle dot and similar to 3.6 M-circle dot with an initial orbital period of similar to 5 days. Based on the fundamental parameters of the A-supergiant (luminosity log L/L-circle dot = 4.1 +/- 0.1 and effective temperature T-eff = 8500 +/- 500 K) and evolutionary tracks of mass-transferring binaries, we found current masses of the gainer M-2 = 8.8 +/- 0.5 M-circle dot and donor M-1 = 0.75 +/- 0.25 M-circle dot. We also modeled the object's IR-excess and derived a dust mass of similar to 5 x 10(-5) Mo in the optically thin dusty disk. The orbital parameters and properties of the H alpha line profile suggest that the circumstellar gaseous disk is predominantly circumbinary. The relatively low mass of the gainer led us to a suggestion that 3 Pup should be excluded from the B [e] supergiant group and moved to the FS CMa group. Overall these results further support our original suggestion that FS CMa objects are binary systems, where an earlier mass transfer caused formation of the circumstellar envelope.

Based on the data of spectral monitoring of the yellow hypergiant V509 Cas performed in 1996-2018 at the 6-m telescope with the spectral resolution of R≥60 000, we studied in detail its kinematic state at various levels of extended atmosphere. No signs of presence of a companion were found. An agreement of radial velocities measured on the permitted and forbidden emissions of metal ions, as well as their strict temporal stability led us to the choice of the systemic velocity of the star Vsys=-63 km/s. The position of forbidden [NII] emissions forming in the circumstellar medium is strictly stable and is systematically shifted by -6 km/s relative to the metal ion emissions. A conclusion on the variation of the [NII] emission halfwidths and intensities (the lines have become narrower and more intense) is made after the observations in 1996 and these parameters did not vary over the next 22 years of observations. The velocities measured from the shortwave FeII(42) absorption components are located in a narrow interval of Vr=-(84÷87) km/s, which indicates the stability of expansion of the upper layers of the atmosphere. The overall atmosphere of the hypergiant is stable, excluding the layers close to the photosphere. The velocity variability in range of Vr=-(52÷71) km/s, identified by the positions of strong metal ion absorption cores, may be a manifestation of pulsations in deep atmospheric layers, where this type of lines are formed.

In the light of new astrometric and available spectroscopic data, the structure and kinematics of the SerOB1A association are discussed and the issue of correcting its boundaries is put.

Based on the data of spectral monitoring of the yellow hypergiant V509 Cas performed in 1996–2018 at the 6-m telescope with the spectral resolution of R ≥ 60 000, we studied in detail its kinematic state at various levels of extended atmosphere. No signs of presence of a companion were found. An agreement of radial velocities measured on the permitted and forbidden emissions of metal ions, as well as their strict temporal stability led to the choice of the systemic velocity of the star Vsys = −63 km s−1. The position of forbidden [NII] emissions forming in the circumstellar medium is strictly stable and is systematically shifted by −6 kms−1 relative to the metal ion emissions. A conclusion on the variation of the [NII] emission halfwidths and intensities (the lines have become narrower and more intense) is made after the observations in 1996 and over the next 22 years of observations, these parameters did not vary. The velocities measured from the shortwave Fe II (42) absorption components are located in a narrow interval of Vr = [−84;−87] kms−1, which indicates the stability of expansion of the upper layers of the atmosphere. The overall atmosphere of the hypergiant is stable, excluding the layers close to the photosphere. The velocity variability in range of Vr = [−52;−71] km s−1, identified by the positions of strong metal ion absorption cores may be a manifestation of pulsations in deep atmospheric layers, where this type of lines are formed.

We present the original technique to solve the problems of stellar astronomy using the highresolution spectroscopy and we describe the result of implementation of this technique to determine if the stellar clusterNGC6613 belongs to the SerOB1A association. From the only one estimation available, the distance toNGC6613 equals 1.3 kpc. It is not clear if the cluster linkedwith the SerOB1A association, the distance to which is 2.1 kpc. For nine stars in the region of NGC6613, the radial velocities were measured from the spectra obtained with the NES spectrometer of the 6-m SAORAS telescope, as well as conducted the two-dimensional spectral classification and found their distances with themethod of spectral parallaxes. Seven of nine stars are referred to the cluster members; the average distance to them is 2.2 ± 0.1 kpc. The distance estimates were controlled using the Na I (1) interstellar line profiles. Thus, it was understood that the cluster NGC6613 is a member of the SerOB1A association and its influence should be taken into account, when describing the star formation in the association.

The phenomenon of spectral mimicry refers to the fact that hypergiants and post-AGB supergiants—stars of different masses in fundamentally different stages of their evolution—have similar optical spectra, and also share certain other characteristics (unstable extended atmospheres, expanding dust–gas envelopes, high IR excesses). As a consequence, it is not always possible to distinguish post-AGB stars from hypergiants based on individual spectral observations in the optical. Examples of spectral mimicry are analyzed using uniform, high-quality spectral material obtained on the 6-m telescope of the Special Astrophysical Observatory in the course of long-term monitoring of high-luminosity stars. It is shown that unambiguously resolving the mimicry problem for individual stars requires the determination of a whole set of parameters: luminosity, wind parameters, spectral energy distribution, spectral features, velocity field in the atmosphere and circumstellar medium, behavior of the parameters with time, and the chemical composition of the atmosphere.

Based on the high spectral resolution monitoring conducted at the 6-m BTA telescope, we study the optical spectrum of the high-latitude variable V534 Lyr. Heliocentric radial velocities Vr corresponding to the positions of all metal absorption components, as well as the Na I D and Hα lines were measured during all the observational sets. The analysis of the velocity field examining the lines of various nature revealed a low-amplitude variability of Vr based on the lines with a high excitation potential, which are formed in deep layers of the stellar atmosphere, and allowed to estimate the systemic velocity of Vsys ≈ −125 kms−1 (Vlsr ≈ −105 kms−1). The distance estimate of d ≈ 6 kpc for the star leads to its absolute magnitude of \(M_V \approx - 5_ \cdot ^m 3\), what corresponds to the spectral classification. The previously undetected spectral phenomenon was revealed for this star: at certain times a splitting of the profiles of low-excited absorptions is observed, reaching ΔVr = 20–50 kms−1. A combination of the parameters: reduced metallicity [Met/H]⊙ = −0.28, high nitrogen abundance [N/Fe] = +1.10, large spatial velocity, high luminosity, a strong variability of the emission-absorption profiles of HI lines, splitting of metal absorptions at different times of observations and the variability of the velocity field in the atmosphere allow to classify V534 Lyr as a pulsating star in the thick disk of our Galaxy.

We study a pulsating variable post-AGB star V534 Lyr = HD172324 based on five high resolution spectra (R = 60000) obtained with the NES echelle spectrograph of the 6-meter Russian telescope (BTA) in 2010 and 2013. Using the atmosphere modeling method and the Kurucz model set, we obtained the effective temperature T-eff = 10500 K, surface gravity log g = 2.5, and microturbulent velocity xi(t) = 4.0 km/s. The underabundance of the iron group elements [Met/H](circle dot) = -0.50 was detected. This fact in combination with high spatial velocity indicates that V534 Lyr does not belong to the disk population. The radial velocity gradient in the V534 Lyr atmosphere is minimum: differential shifts of lines are close to measurement errors. The spectral class A0 Iab corresponds to the distance to V534 Lyr, d approximate to kpc.

We present the results of our study of two massive stars, V1302 Aql (IRC+10420) and GR 290 (M33/V532, Romano's Star), with different initial masses but now approaching the region of Wolf-Rayet stars on the Hertzsprung-Russell diagram, one from the yellow hypergiants side and the other from the Luminous Blue Variables side.

Based on long-term spectral monitoring with high spectral resolution, the optical spectrum of the weak central star of the IR source RAFGL 5081 has been studied for the first time. The spectral type of the star is close to G5–8 II, and its effective temperature is T eff ≈ 5400 K. An unusual spectral phenomenon was discovered: splitting of the profiles of broad, stationary absorption lines of medium and low intensity. The heliocentric radial velocities V r of all components of metal absorption lines, the Na I D lines, and the Hα line were measured for all the observation epochs. The constancy of the absorption lines rules out the possibility that the line splitting is due to binarity. The radial velocities of the wind components in the profiles of the Na I D and Hα lines reach −250 and −600 km/s, respectively. These profiles have narrow components, whose number, depth, and position vary with time. The time variability and multicomponent structure of the profiles of the Na I D and Hα lines indicates inhomogeneity and instability of the circumstellar envelope of RAFGL 5081. The presence of components with velocity V r (IS) = −65 km/s in the Na I (1) lines provides evidence that RAFGL 5081 is located behind the Perseus arm, i.e, no closer than 2 kpc. It is noted that RAFGL 5081 is associated with the reflection nebula GN 02.44.7.

To explain the nature of the anomalously high reddening (Av~10 mag) towards one of the most luminous stars in the Galaxy - Cyg OB2 #12 (B5 Ia-0), also known as MT304, we carried out spectro-photometric observations of 24 stars located in its vicinity. We included five new B-stars to the members of Cygnus OB2, and for five more photometrically selected stars we spectroscopically confirmed their membership. We constructed the map of interstellar extinction within 2.5 arcmin radius and found that interstellar extinction increases towards MT304. The increase of reddening suggests that the reddening excess may be caused by the circumstellar shell ejected by the star during its evolution. We also report the detection of a second component of MT304, and discovery of an even fainter third component, based on data of speckle interferometric observations taken with the Russian 6-m telescope.

We present the results of a study of spectral features and the velocity field in the atmosphere and circumstellar envelope of the yellow hypergiant V1302 Aql, the optical counterpart of the IR source IRC+10420, based on high-resolution optical spectroscopic observations in 2001-2014. We measured heliocentric radial velocities of the following types of lines: forbidden and permitted pure emission, absorption and emission components of lines of ions, pure absorption (e.g. He i, Si ii) and interstellar components of the Na i D lines, K i and diffuse interstellar bands (DIBs). Pure absorption and forbidden and permitted pure emission, which have heliocentric radial velocities V-r = 63.7 +/- 0.3, 65.2 +/- 0.3 and 62.0 +/- 0.4 km s(-1), respectively, are slightly redshifted relative to the systemic radial velocity (V-sys 60 km s(-1)). The positions of the absorption components of the lines with inverse P Cyg profiles are redshifted by 20 km s(-1), suggesting that clumps falling on to the star have been stable over all observing dates. The average heliocentric radial velocity of the DIBs is V-r(DIB) = 4.6 +/- 0.2 km s(-1). A H alpha line profile with the red peak slightly stronger than the blue one was observed only once, on 2007 November 24. Comparison of pure absorption lines observed in 2001-2014 with those in earlier data does not show noticeable variations. The kinematic picture in the atmosphere was stable for observations during 2001-2014. Our results as a whole let us conclude that the hypergiant has reached a phase of slowing down (or termination) of effective temperature growth and is currently located near the high-temperature boundary of the Yellow Void in the Hertszprung-Russell diagram.

The Cyg OB2 stellar association hosts an entire zoo of unique objects, and among them – an enigmatic star Cyg OB2 No. 12 (Schulte 12, MT 304). MT 304 is enigmatic not only due to its highest luminosity (according to various estimates, it is one of the brightest stars in the Galaxy), but also because its reddening is anomalously large, greater than the mean reddening in the association. To explain the nature of anomalous reddening (AV ≃ 10 mag) of MT 304, we carried out spectrophotometric observations of 25 stars located in its vicinity. We mapped interstellar extinction within the 2.5 arcmin radius and found it to increase towards MT 304. According to our results, the two most reddened stars in the association after MT 304 are J203240.35+411420.1 and J203239.90+411436.2, both located about 15 arcsec from it. Interstellar extinction AV towards these stars is about 9 mag. Our results favor the hypothesis of the circumstellar nature of reddening excess. In the second part of the paper we present the results of our modeling of MT 282 (B1 IV) and MT 343 (B1 V), which belong to the older population of the association and have ages greater than 10 Myr.

An atlas of spectra of the unique high luminosity objects MWC 314 and IRC+10420 taken with the CCD echelle spectrograph (R=15000) at the prime focus of the 6-m telescope of SAO is presented. About 320 emission and absorption features of stellar, circumstellar and interstellar nature are identified in the interval between 4790 and 7520 Å. Their relative intensities and radial velocities are given and the distinctions of their profiles are discussed.

To explain the nature of the high reddening (Av~10 mag) towards one of the most luminous stars in the Galaxy - Cyg OB2 #12 (B5 Ia-0), also known as MT304, we carried out spectro-photometric observations of 24 stars located in its vicinity. We included five new B-stars among the members of Cygnus OB2, and for five more photometrically selected stars we spectroscopically confirmed their membership. We constructed the map of interstellar extinction within 2.5 arcmin radius and found that interstellar extinction increases towards MT304. According to our results the most reddened OB-stars in the association after MT304 are J203240.35+411420.1 and J203239.90+411436.2, located about 15 arcsec away from it. Interstellar extinction towards these stars is about 9 mag. The increase of reddening towards MT304 suggests that the reddening excess may be caused by the circumstellar shell ejected by the star during its evolution. This shell absorbs 1 mag, but its chemical composition and temperature are unclear. We also report the detection of a second component of MT304, and discovery of an even fainter third component, based on data of speckle interferometric observations taken with the Russian 6-m telescope.