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Thirty three spectra of the Polaris system obtained in August–December 2019 and February–April 2020 at the 0.81m telescope of the Three College Observatory (TCO, North Carolina, USA) were used to determine the radial velocities (RV) and effective temperature of the Cepheid Polaris Aa. These new data have been added to the entire Polaris system RV data collection (over 2,500 measurements) to compute a new orbit of the Polaris Aa companion. Furthermore we have used our eight observational datasets taken in 2015–2020 and eight datasets taken in 2011–2018 by Anderson (2019) to check for possible influence of the orbital motion of Polaris Ab on the Polaris Aa pulsational activity. It was found that the mean pulsational period in 2015–2020 was quite stable (3.976±0.012 days), while the pulsational amplitude showed evident changes: a growth before HJD 2457350 with a following decrease. This fact could be due to the Polaris Ab passing through the periastron.

We present the results of a spectro- scopic and photometric investigation of 18 probable members of the open cluster Collinder 220, which contains the Cepheid UW Car. Besides the Cepheid, we studied tree K-giants, two B-giants, and twelve B-A-F main sequence stars. Radial velocities (RV), vsini, T eff , and logg were determined using spec- troscopic model fitting and atmosphere models. We have derived color-excesses, reddenings, and intrinsic colors for these stars using their T eff and logg from comparison to the atmosphere models, especially for hot stars. Proper motions, RV, and the GAIA DR2 2018 parallaxes allowed us to determine their membership in the cluster and absolute magnitudes. We found that seven stars along with the Cepheid can be the cluster members with a high confidence. The parallaxes and reddenings of the 7 confident cluster members led to the distances in a range of 1900–2800 pc, while the other stars are probably foreground objects. All the members have [Fe/H] near 0.1 dex. The B-giant HD90435 located near the cluster’s “turn-off” point has a low projected rotational veloc- ity, and this fact allows us to determine its chemical composition to compare with that of the Cepheid UW Car. The CNO abundances of HD90435 are nearly solar, while the Cepheid shows a deficit of carbon, an overabundance of nitrogen, a nearly solar oxygen, and an overabundance of sodium. The confident cluster member, K-supergiant CPD −57 ◦ 3199, has CNO- and Na abundances close to those of UW Car.

We present the results of a spectro- scopic and photometric investigation of 20 objects from the open cluster Collinder 394, which contains the Cepheid BB Sgr. Besides the Cepheid, we studied tree K-giants, four B-giants, and twelve B-A-F main sequence stars. Radial velocities (RV), vsini, T eff , logg, were determined using spectroscopic model fitting and atmosphere models. We have derived the color-excesses, reddenings, and intrinsic colors for these stars using their T eff and logg from compar- ison to the atmosphere models, especially for hot stars. Proper motions, RV and GAIA DR2 2018 parallax/distance values for these stars allowed us to determine their membership in the cluster and absolute magnitudes. We found that seven stars do not belong to the cluster. The parallaxes and reddenings of 13 confidently cluster members led to the distances in a range of 630–800 pc, although the majority of them (8 objects) are located at a mean distance of 657.7±66.7 pc, and 5 objects with the Cepheid could probably belong to the cluster’s corona. All the members have [Fe/H] near 0.1 dex. The main sequence B-star No. 76 (HD 174307) has a low rotational velocity projection, and this fact allows us to determine its chemical composition to compare with that of the Cepheid BB Sgr. Its CNO and Na abundances are close to the solar one, while the Cepheid show a deficit of carbon, an overabundance of nitrogen, nearly solar oxygen, and an overabundance of sodium. Three foreground K-giants have different C abundances (from a deficit to the solar), and Na (from the solar to an overabundance) as well as a solar-like O content. The foreground F7-8 V star No. 75 (CPD −20 ◦ 7218) was revealed to be a Li-rich star, while the A7 V star No. 69 (BD −20 ◦ 5290) has an anomalous deficit of CNO with overabundances of some α, r- and s-process elements.

We investigate evolutional status of cepheid V1033 Cyg in this work, its period of light variation consists 4 d .94 and the star is a real candidate on first crossing of instability stripe (IS) (as well as α of UMi). At first crossing of instability stripe, that lasts all close 1000 years, cepheids demonstrate the rapid increase of period, sometimes is a presence of strong line of lithium 6707 ˚ A. Such objects knows only four in our Galaxy, one of them - V1033 Cyg. During included in a instability stripe amplitude of pulsations headily grows from a zero to some permanent size, and on leaving from (IS) - again falls to a zero. For verifica- tion this phenomenon in the Astronomical observatory of Odesa National University (Ukraine) on the 48-cm telescope AZT-3, equipped by CCD photometer with the optical sensor Sony ICX429ALL, a 1864 measuring of light V1033 Cyg were done in the filter of V and 713 in the filter R, that are partly presented in the Table. 1 and Fig. 2, and fully accessible to address http://cdsarc.ustrasbg.fr/viz-bin/cat. Considerable change of amplitude it is not got by us. The position of cepheid is certain by us in the (IS) - it appeared that star is near her center. In this phase evolutional to development and it must not be observed considerable change of amplitude (color index). The light curves, effective temperature and luminosity of V1033 Cyg are consistent with fundamental mode pulsation for a classical Cepheid on the center of the instability strip.

We present the results of an analysis of 20 spectra of α UMi (Polaris) obtained in September 2018 – January 2019 using 0.81m telescope of the Three College Observatory (TCO), North Carolina, USA. Frequency analysis displays an increase of the pulsational period up to 3.68 min in comparison to the August - December 2017 - January - May 2018 observational sets, and it come to 3.973216 days. The systemic velocity (γ – velocity) is equal to −11.75 kms −1 . The radial velocity amplitude rose to 3.50 kms −1 and actually returned to the previous values of 3.43, 3.31, and 3.81 kms −1 , respectively, found from the August - December 2016, January - March 2017 and August - December 2017 sets. The radial velocity’s amplitude growth tendency still remains. The average T eff = 6051±22 K shows a growth toward the value found from the 2005 – 2007 observational sets and probably has a tendency toward the T eff growth. The joint TCO and Hermes radial velocity measurements during the last four years show the changes of Polaris’ pulsational amplitude.

We present the results of an analysis of the spectra of nine so called Polaris cluster A−FV stars obtained during 2016 - 2018. Radial velocities (RV) and GAIA DR 18 parallaxes-distances for these stars allow us to determine their membership in the cluster and to construct its 3D kinematic model. However Teff for four stars determined spectroscopically give cause for doubts about the GAIA DR 18 parallaxes accuracy. The comparison between their MV and distances with the those from Pecaut & Mamajek (2013) calibrations shows significant differences for the objects with parallaxes less than 8 mas. The differences in distances increase exponentially with decreasing parallax. These facts indicate an unreliability of the GAIA DR2 parallx measurements of less than 10 mas. We estimated the distance to Polaris B to be 104.2 pc.

We present the results of a spectroscopic and photometric investigation of 15 objects from the open cluster NGC 5662, which contains the Cepheid V Cen. Besides the Cepheid, we studied one G-supergiant, two K-giants, four B-giants, and seven main sequence stars. Radial velocities (RV), v sin i, Teff, log g, and [Fe/H] were determined using model fitting. We have derived the color-excesses, reddenings, and intrinsic colors for these stars to determine their true Teff and log g from comparison to the atmophere models, especially for hot stars, and to determine their absolute magnitudes. RV and GAIA DR2 2018 parallax/distance values for these stars allowed us to determine their membership in the cluster and to construct it 3D kinematic models. These parallaxes and reddenings led to the distances in a range of 700– 875 pc, while photometric MV gave the distances of 550–660 pc. Two objects from our list were found to be non-members of the cluster, and two other objects to be background stars. All members have [Fe/H] = −0.1±0.04 dex. The main sequence stars and B-giants have abundances of C, N, and Na close to the solar one, while the cool supergiants and giants show a deficit of carbon, an overabundance of nitrogen, and a small overabundance or close to the solar sodium content. Two Li-rich K-giants, HD 127733 and HD 127753, were discovered in the cluster.

We have described the method of investigation of the diffuse interstellar band (DIB) at 6202 ˚ A. This DIB is seen in the spectra of cepheid stars, and it is blended with two stellar lines of Ce II (6201.773 ˚ A) and Ni I (6204.6 ˚ A). After removal of the blending lines of ionized cerium and neutral nickel, we can determine the equivalent widths (EW) of the DIB. This procedure can be applied for the sample of cepheids (with well known distances), which enables one to construct the map of the organic matter distribution in the Galactic disc and use these values to investigate the E(B–V)–DIB EW relation. The relation found from Cepheids matches that found in B stars. This relation can help to find the reddening for newly discovered Cepheids without extensive photo- metric data, and thus determine their distances. The relation between E(B–V) and the DIB EW does not yield precise reddening values. It is not a substitute for better photometric or spectroscopic methods. At best, it is indicative, but it provides some information that may not be otherwise available.

The chemical composition of three classical cepheids δ Cep, η Aql and ζ Gem, has been investigated by using model atmospheres' method. It is shown that Na and Mg are overabundant (≈+0.35 dex), C and 0 are slightly underabundant (≈ -0.20 dex) relative to the Sun. The atmospheric abundances for other elements are close to the solar composition. The low limit of helium atmospheric abundance in classical cepheids, derived from the spectrum of a physical companion of δ Cep (δ Cep-C, B7 IV, Teff =13250 K, log g=3.85, Vt=0.0 km/s), is [He/H]= -0.13. The comparison of chemical composition in the atmospheres of δ Cep cepheid and its companion obviously illustrates the variation in abundance of CNO elements during the cepheid evolution. If the primary C, 0 abundance for cepheid is solar-like (as the chemical composition of a companion corresponds to initial composition of the cepheid), then after red- supergiant phase (phase of dredge-up) we can observe the cepheid as a star being deficient in C and 0.

We present precise effective temperatures (Teff) of 110 F-K supergiants determined from the method of line depth ratios. For each star, we have measured the line depths a large number of spectral lines of low and high excitation potentials and established ~ 100 relations between Teff and their ratios. These relations have been calibrated against previously published accurate temperature estimates. The range of application of the method is 4000-7000 K (F2-K4). The internal error for a single calibration is less than 110 K, while the combination of all 100 calibrations reduces the uncertainty to only 5-35 K (1 sigma). A big advantage of the line ratio method is its independence on interstellar reddening, spectral resolution, and line broadening due to rotation or microturbulence.

The new spectral energy distributions Eλ for 360 stars in wavelength region from λ 330 to λ 725 nm are given. The observations for "relatively-absolute" stellar spectrophotometry were obtained at high-altitude astronomical station “Terskol” of Odessa Astronomical Observatory in 1973-1988 years. The station was located at a height of 3100 m in the Caucasus. The method of "relatively-absolute" spectrophotometry was used to obtain the spectral energy distribution. The comparison stars were α Lyr, β Ari, γ Ori, α Leo, ηUMa, α Aql, α Peg, β CMi, θ Leo and α Oph. The Eλ of all stars of comparison were reduced to α Lyr (except βCMi and θ Leo — their spectral distribution was reduced to stars βAri and α Leo respectively). The analysis of various mistakes was made and these were taken into account. The comparison with other Catalogues of the former USSR was made. It should be noted that the technique of observing and obtaining was unified. Similar optical and mechanical systems were used as well as analogous procedures of observations of stellar radiation and subsequent calculations. Only the register electronic devices were modified. The random errors of results for all the Catalogues are nearly equal 2 ÷ 3 % (to 5%) in the visual range of a spectrum and 5 ÷10% at the edges of the observed spectral bands – ultraviolet and near infrared regions. However, the random errors of spectrophotometry results of various authors have large discrepancies (up to several dozens (!) of percents sometimes).

Three classical Cepheids in galactic open clusters (CF Cas, DL Cas and WZ Sgr) were investigated, using high-resolution CCD spectra. Their Teff and EB-V estimations have a good agreement with photometrically determined ones. CF Cas and DL Cas have metallicity values, close to those of the Sun, whereas WZ Sgr has overabundant metallicity content with Z=0.029. Chemical abundance data show that they are the post first dredge-up stars. C and O content and ages have a good agreement with the theoretically predicted values. All these objects have a good fit with the PL relation for galactic Cepheids.

We present results of preliminary determinations of abundances of heavy elements in three metal-poor stars: HD37828, HD44008, HD221170. Careful comparison of observed and synthetic spectra permit us to increase the number of lines heavy elements identified in observed spectra. Results will be used for determinations of the abundances of these elements with the spectrum synthesis method in these and other metal-poor stars.

First Cepheids observations using echelle-spectrograph HRS fed by Southern African Large Telescope (SALT) were realized during 2016. All spectra have been obtained in the medium resoltion mode (R≈31000–41000) wth high S/N ratio near 50–220. All data were processed using package developed by authors based on the standard system of astronomical data reduction MIDAS. Using new echelle data we found the atmosphere parameters and chemical composition for 30 faint Cepheids of southern hemisphere, where for the most of theses stars these results we obtained for the first time. 28 stars are Cepheids after the first-dredge up stage, while ASAS 075842-25336.1 and ASAS 1131714-6605.0 having remarkable Li I 6707.8 Å absorption line and anomalous CNO and Na content could be consider as first crossing of the Cepheids instability strip.

We present the results of an analysis of 49 spectra of α UMi (Polaris) obtained during August – December 2016 and January – March 2017. Frequency analysis displays an unexpected decrease of the pulsational period up to 17.3 min in comparison to the 2015 observational set. The radial velocity amplitude was reduced to 3.43 km s−1 in 2016 and to 3.31km s−1 in the beginning of 2017 in comparison with 4.16 km s−1 in 2015. This result is also unexpected, because during the last decade a gradual amplitude growth has been observed. The average Teff = 6021 K determined from the 2016–2017 data is close to the values determined for the 2001–2015 set.

We have carried out the detailed analysis of 350 high-resolution spectra of FGK dwarfs and giants. Abundances of Fe, Si, Ca and Ni have been determined under LTE approximation, whereas abundances of Mg have been determined under NLTE approximation. Spatial velocities with an accuracy better than 1 km/s-1, as well as orbits, have been computed for dwarfs (or all) stars. They have been used to define 2 subsamples kinematically representative of the thin disk and the thick disk in order to highlight their respective properties. A transition occurs at [Fe/H] = -0.3. Stars more metal-rich than this value have a flat distribution with Zmax

We report about the discovery of two lithium Cepheids in the Galaxy, based on observations made with the echelle spectrograph of the Apache Point Observatory. We have used high- resolution, high signal-to-noise spectra to determine abundances of chemical elements in 16 classical Cepheids. Only two of our program stars show a lithium line, RX Aur and YZ Aur (RX Aur has been also classified by us as a new non-radial pulsator). For the others, including the stars with [N/C] < 0.2, Li is depleted up to

We present the results of an analysis of 21 spectra of alpha UMi (Polaris) obtained in September – December 2015. Frequency analysis shows an increase of the pulsation period up to 8.6 min in comparison to the 2007 observational set. The radial velocity amplitude comes to 4.16 kms-1, and it approximately twice the one found in 2007. The average Teff = 6017 K, and it is close to the value determined for the 2001–2004 set. Therefore Polaris moves to the red edge of the Cepheid instability strip (CIS).

Spectroscopic observations of EV Sct obtained on 4m telescope at KPNO showed that the secondary component is probably situated within the instability strip (Kovtyukh & Andrievsky, 1999). Some observers (Pel, 1976; Mermilliod, 1987) have noted a signicant data scattering on the light curve. Therefore the companion of EV Sct perhaps is a small amplitude variable star. We present results of photoelectric observations of the EV Sct.

A thorough study of the correlation between P1=P0 ratio, fundamental period, and chemical composition (abundances of metals that compose Z) was conducted to investigate the significance of the iron-peak elements on the ratio. The results suggested a more accurate P1=P0 ratio that can be useful as an alternative means of determining a beat Cepheid’s metallicity. Metallicities for a large sample of stars were analysed using the suggested ratio. The metallicity distribution function for the Magellanic Clouds projected on the celestial sphere was constructed for the first time, and several stars with anomalous metallicities were detected. The average metallicities of the Magellanic Clouds were also obtained independently: –0.30 dex for the Large Magellanic Cloud (LMC) and –0.49 dex for the Small Magellanic Cloud (SMC). The [Fe=H] values for two newly-found bimodal Cepheids in the Galactic bulge were estimated: –0.39 dex for OGLE-BLG-CEP-03 and –0.29 dex for OGLE-BLG-CEP-21.

Thirty three spectra (one spectrum for the each of 33 observational nights) have been performed to coverall pulsational period of the 35.5-days Cepheid l Car. Due to these data we have obtained for the first time the detailed curves of effective temperature, gravity and turbulent velocity. Curves of gravity and turbulent velocity show complicated changes, connected probably with dynamics of extensive Cepheid’s atmosphere. The mean atmosphere parameters of l Car are: Teff =4984±15K; log g = 1.13; Vt =6.67kms−1. Having a solar metallicity [Fe/H]=+0.02dex, this Cepheid demonstrate sudden results for the ”key” elements abundances of yellow supergiants evolution, – all they are close to the solar ones. In this case l Car resembles to SV Vul, – Cepheid with 45-days pulsational period and nearly like spectral type. It is possible that l Car is an object crossing the Cepheids instability strip for the first time. The content of other elements is close to solar one too.

The comparative analysis of the abundances of α-process elements, elements of the rapid and the slow neutron capture and iron in the open stellar clusters, field Cepheids, and also in red giants and dwarfs of the thin disk has been performed. The found distinctions and the revealed regularities are attracted for clarification of the history of star formation in the thin disk of the Galaxy.

Four high-resolution spectra of the double-mode Cepheid V371 Per, obtained for the first time, showed the presence of the abnormally strong Li i 6707.76 Å line. Our analysis of the light element abundances indicates that the star did not go through the evolutionary dredge-up stage. Large distance from the galactic plane and the low metallicity suggest that V371 Per may belong to the thick disc (or to the halo) of the Galaxy, which is consistent with its low metallicity [Fe/H]=-0.42 and the enhancement of the α- and s-elements relative to iron. Line splitting is observed in one of the spectra, which can be due to the non-radial pulsations.

Radial gradient of relative amplitude of the light variation FV for galactic classical Cepheids is found. The gradient has different signs for two cases: P > 8d and P < 8d. For P > 8d the gradient is negative. This gradient is caused by gradient of helium content in the primordial clouds, where Cepheids were born. In agreement with theoretical calculations, the amplitude increase with an increasing of the helium content. For this dependence the following calibration was obtained: [He/H] = (FV - 0.54) dex Y= 0.55FV - 0.03 In case P < 8d the amplitude (and also asymmetry parameter M-m) is mainly affected by metallicity.

High precise temperatures (σ = 10 - 15 K) have been determined from line depth ratios for a set of 182 F-K field dwarfs of about solar metallicity (-0.5 < [Fe/H] < +0.4), based on high resolution (R=42 000), high S/N echelle spectra.

We have determined 28 relations between M ν, T eff and line depths ratios Rλ1/R λ2. These relations have been used for the estimation of the absolute magnitudes M ν of 56 FGK supergiants with an error 0.05-0.30 mag (Table 1). The application range is F0-K0, luminosity classes I and II.

We derive accurate, homogeneous atmospheric parameters (Teff , log g, Vt, [Fe/H]) for 74 FGK non-variable supergiants and for 30 classical cepheids in 302 pulsation phases based on the highresolution, high signal-to-noise echelle spectra. The extremely high precision of the effective temperature determination (10-30 K) is achieved by using the line- depth ratio method. These parameters are correlated with unreddened B-V colour index compiled from the literature for investigated stars to obtain an empirical relationship of the form (B-V )0 = 57.984 - 10.3587(logTeff )2 + +1.67572(logTeff )3 - 3.356logg + 0.0321Vt+ +0.2615[Fe/H] + 0.8833(logg)(logTeff ) This expression have been used for the estimation of the colour excesses E(B-V) of individual supergiants and classical cepheids with an error 0.05 mag, which matches precision of the most sophisticated photometric techniques. The application range is F0-K0, luminosity classes I and II. Considering the large distances of supergiants, this method opens up a possibility for the large-scale extinction mapping of the Galaxy, with sensitivity down to 0.1-0.2 mag.

Atmospheric parameters (Teff , log g, [Fe/H], Vt), Li, and volatile (O, Na, Al, Zn) and refractory (Si, Ti, V, Cr, Co and Ni) element abundances in 133 stars belonging to the low part of MS have been determined. Among them about 30 stars are the variable stars of BY Dra type, for which the determination of the chemical composition was made for the first time. The effective temperatures Teff were estimated by the line depth ratio method. The surface gravities log g were determined by two methods (ionization balance of iron and using parallaxes). The abundances of lithium and oxygen were determined by the calculation of synthetic spectrum. The comparison of volatile and refractory element abundances in variable stars and other stars was made. We have found that the behaviour of the abundances of the majority of elements in MS stars and spotted stars does not differ. The Li is detected in 65 BY Dra stars and in 26 of MS stars. The Li abundance in variable stars is higher than in MS dwarfs.

HQ Car is listed as an δ Cep star (DCEP) in the GCVS. High-resolution spectra of HQ Car showed the presence of the Balmer and HeI 5876 Å emissions. The light curve shows steeper rise than decline, and there is evidence for the presence of a bump in the descending branch around the phase of 0.4. From considerations of the period, spectral type, presence of the bump, Helium and Balmer emissions we conclude that HQ Car belongs to the W Vir class of Type II Cepheids

The isotopic abundances of magnesium in the star of thin disk of Galaxy with various chromospheric activity were studied. We use the new data about molecular constants of radiation for isotopes 24Mg, 25Mg, and 26Mg. Values close to solar ratios are generally found.

We describe an effective method of investigation of the Diffuse Interstellar Bands (DIBs) in the spectra of Cepheid stars. DIBs are believed to originate from the absorption of such carriers as polycyclic aromatic hydrocarbons in the interstellar gaseous clouds located between an observer and the stars whose spectra were recorded. We performed a detailed consideration of the DIB at 6613 A in our sample of spectra for more than 250 stars. The quantitative characteristics of the DIB absorption features will be studied in connection with the interstellar absorption data, and after that, they will be used in the mapping of the Galactic disc.

The spectra of OU Gem were obtained with the fiber-fed echelle spectrograph SOPHIE at the 1.93-m telescope of the Observatoire de Haute- Provence (France). The temperatures of components of the system were defined and are equal to 5013 ± 15 K and 4486±50 K for primary (A) and secondary (B) components, accordingly. The rotation velocity of components are measured: for primary component it is equal to 5.1±1 km/s and 6.2 ± km/s for the secondary one. The definition of radial velocities of components by LSD profile method and redetermination of spectral orbital elements were carried out. New absolute parameters of components were obtained too.

Abundances of neutron-capture (n- capture) elements in the stars belonging to thin and thick disks are obtained. The separation of thin and thick stars on kinematic criterion was made early. The spectra were obtained with the ELODIE spectrograph at the 1.93-m telescope of the Observatoire de Haute Provence (France). The determination of elemental abundances was carried out in LTE assumption by model atmosphere method, for Ba and Eu taken into account the hyperfine structure. The dependences of n-capture element abundances on metallicity for thin and thick disks are presented.

Abundances of Y, Zr, La, Ce, Nd, and Sm have been obtained under LTE approximationss. The program stars were observed at high resolution, high signal to noise ratio with the ELODIE echelle spectrograph (OHP, France). Among them more than 30 stars are active stars with a fraction of BY Dra and RS CVn type stars. Comparison of the behavior of n-capture elemental abundance in active and non active stars was made.

The spectra of studied stars were obtained with the ELODIE spectrograph at the 1.93-m telescope of the Observatoire de Haute Provence (France). The determination of Cu and Zn abundances was carried out in LTE assumption by model atmosphere method, for Cu the hyperfine structure was taken into account. Cu and Zn abundance trends for thin and thick disk's stars are presented.

Abundances of Na, Al, Ca, in the stars of galactic disks are obtained. The separation of thin and stars on cinematic criterion was made early. The behavior of chemical element abundances with metallicity for studied stars was presented.