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Документ CHEMICAL COMPOSITION AND ATMOSPHERE PARAMETERS OF THE DOUBLE-MODE CEPHEID U TRA(Astroprint, 2013) Usenko, I. A.; Kniazev, A. Yu.; Berdnikov, L. N.; Kravtsov, V. V.Four high-resolution spectra of the doble-mode Cepheid U TrA have been obtained during its pulsational period. For the first time, we obtained accurate atmosphere parameters and the chemical abundance of a number of elements, in particular of sodium, magnesium, and aluminium. We estimated the mean Teff = 6085 29 K, log g = 2.00 0.15, and Vt = 3.90 0.25 kms -1 . A deficit of carbon ([C=H] = –0.35 0.23 dex), overabundance of both sodium ([Na=H] = +0.15 0.25 dex) and aluminium ([Al=H] = +0.30 0.32 dex) are typical for Cepheids passing through the first dredge-up phase. The abundance of iron ([Fe=H] = +0.01 0.15 dex) is very close to the solar one. Moreover, we find that -elements, those of Fe-group, as well as ”light”- and ”heavy”-, s- and rprocess elements, all of them have abundances close to solar values, too, excepting maybe several elements with slight enhance or deficit.Документ Effective temperature and radial velocity of the small-amplitude cepheid polaris (a UMi) in 2015(Одеський національний університет імені І. І. Мечникова, 2016) Usenko, I. A.; Kovtyukh, Valery V.; Miroshnichenko, A. S.; Danford, S.We present the results of an analysis of 21 spectra of 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 kms1, 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).Документ Effective temperature and radial velocity of the small{amplitude cepheid polaris (α UMi) in 2015(Одеський національний університет імені І. І. Мечникова, 2016) Usenko, I. A.; Kovtyukh, Valery V.; Miroshnichenko, A. S.; Danford, S.We present the results of an analysis of 21 spectra of 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 kms1, 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).Документ FUNDAMENTAL PARAMETERS AND CHEMICAL COMPOSITION OF CEPHEID X SGR.(Astroprint, 2012) Usenko, I. A.; Kniazev, A. Yu.; Berdnikov, L. N.; Kravtsov, V. V.Five high-resolutioned spectra of unusual Cepheid X Sgr have been obtained during its pulsational period. For the first time we obtain accurate fundamental parameters and abundances of chemical elements, in particular of sodium, magnesium and aluminium. We estimate the mean Teff = 6143 30 K; log g = 2.00; Vt = 4.35 kms -1 . The estimated effective temperature and surface gravity are relatively high compared to the typical values characteristic of Cepheids with pulsational period around 7 days. A deficit of carbon ([C/H] = -0.26 0.04 dex), overabundances of sodium ([Na/H] =+0.31 0.04 dex) and aluminium ([Al/H] = +0.21 0.08 dex) are typical for Cepheids passing through the first dredge-up phase. However, an obvious overabundance of magnesium([Mg/H] = +0.19 0.04 dex) is unusual. The abundance of iron ([Fe/H] = -0.02 0.01 dex) is very close to the solar one. Abundances of α - elements, (those of Fe-group, as well as ”light ” and ”heavy”, s- and r-process elements) are comparable to the solar values, except for several elements showing slight over- or underabundances.Документ H a LINE AS AN INDICATOR OF ENVELOPE PRESENCE AROUND THE CEPHEID POLARIS Aa ( UMi)(Astroprint, 2015) Usenko, I. A.; Miroshnichenko, A. S.; Klochkova, V. G.; Tavolzhanskaya, N. S.We present the results of the radial velocity (RV ) measurements of metallic lines as well as H (H ) obtained in 55 high-resolution spectra of the Cepheid UMi (Polaris Aa) in 1994–2010. While the RV amplitudes of these lines are roughly equal, their mean RV begin to differ essentially with growth of the Polaris Aa pulsational activity. This difference is accompanied by the H core asymmetries on the red side mainly (so-called knifelike profiles) and reaches the value of 8–12 km/s in 2003 with subsequent decrease to 1.5–2 km/s. We interpret so unusual behaviour of the H line core as dynamical changes in the envelope around Polaris Aa.Документ HD 121135: features of its chemical composition(Одеський національний університет імені І. І. Мечникова, 2020) Mishenina, T. V.; Usenko, I. A.; Kniazev, A. Yu.; Kovtyukh, Valery V.; Ковтюх, Валерій В.Low metallicity star HD121135 ([Fe/H] = -1.5) have been investigated spectroscopically. Its atmospheric parameters and elemental abundances have been determined, including elements of neutron (n-) capture processes, which are the keys in the study of early Galaxy enrichment. Na, Mg, Ni, Co, Sr, Y, Zr, Mo, Ba, La, Ce, Pr, Sm, Eu, Gd, Dy, Ho, Os, Th abundances were calculated using the synthetic spectrum method, factoring in the hyperfine structure (HFS) for the Eu II lines. Si, Ca, Sc abundances were determined using the equivalent widths of their lines. The carbon content was computed by the molecular synthesis fitting for the region of CH (4300-4330 ÅÅ). For the abundances determinations of C, Na, Mg, Ba, and Th the NLTE corrections have been applied. We have determined for the first time the abundances of several n-capture elements and found that the behaviors of these elements do not show a significant trend with increasing atomic number. The elements ratios of [Eu/Fe] = 0.06, [Ba/Eu] = 0.13, [Sr/Ba] = - 0.05 do not support the HD121135 status as a r-process enrichment star. We have obtained the thorium abundance [Th/Fe] = 0.26. The carbon content confirms the effect of canonical additional mixing in this star.Документ MAGNETIC FIELD OF POLARIS(Astroprint, 2010-07) Usenko, I. A.; Bychkov, V. D.; Bychkova, L. V.; Plachinda, S. I.25 effective magnetic field (Be) estimates of Polaris (α UMi) were obtained from July 1983 to December 2005 using 1m Zeiss and 6m BTA telescopes of SAO RAS, equipped by magnitometers. These data with added 7 ones from Borra et al.(1981), obtained in 1980 show that magnetizing force of Polaris vary from +162 to - 109 Gauss do not depend on the changes of pulsational amplitude, but Fourier analysis reveal variability of magnetic field with period of 3.97586 days, close well with its pulsational period of 3.96961 days.Документ Manifestation of stellar evolution in metal-deficient stars(Одеський національний університет імені І. І. Мечникова, 2023) Mishenina, Tamara V.; Usenko, I. A.; Kniazev, A. Yu.; Gorbaneva, T. N.; Мішеніна, Тамара ВасилівнаMetal-poor stars allow us to establish the early history of the Milky Way, furthermore the stars on advanced evolution stage (e.g. giants, AGB stars etc.) give the opportunity to research the peculiarities of stellar evolution at low metallicity. On the base of the 11m Southern African Large Telescope (SALT) spectra obtained using HRS fibre-fed echelle-spectrograph during 2018 -2020, the atmospheric parameters and elemental abundances of four metal-poor stars HE 1523-0901, HD 6268, HD 121135, and HD 195636 ( [Fe/H] ~ -1.5 – -3.0) have been obtained. The iron abundance was determined based on the equivalent widths of absorption lines. The carbon abundance was obtained using the molecular synthesis fitting for the CH (4300-4330 ÅÅ) region, nitrogen from CN at 3883 Å, oxygen from [O] line at 6300 Å and IR triplet at 7770 Å The relationship between the chemical enrichment of stars and their stellar evolution is considered. It may be associated with the processes of mixing inside the stars, and the mechanisms of matter transfer during stellar evolution.Документ MULTIPHASE SPECTROSCOPIC OBSERVATIONS OF THE LONG-PERIOD CEPHEIDS l CARINAE(Astroprint, 2013) Usenko, I. A.; Kravtsov, V. V.; Kovtyukh, Valery V.; Berdnikov, L. N.; Kniazev, A. Yu.; Chini, R.; Fokin, A. B.Thirty three spectra (one spectrum for the each of 33 observational nights) have been performed to cover all 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, connceted probably with dynamics of extensive Cepheid’s atmosphere. The mean atmosphere parameters of l Car are: Teff = 4984 15 K; log g = 1.13; Vt = 6.67 km s−1. Having a solar metallicity [Fe/H] = +0.02 dex, 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.Документ Pulsational activity of The Small-amplitude Cepheid polaris (a UMi) in 2016-2017(Одеський національний університет імені І. І. Мечникова, 2017) Usenko, I. A.; Kovtyukh, Valery V.; Miroshnichenko, A. S.; Danford, S.We present the results of an analysis of 49 spectra of а 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 kms-1 in 2016 and to 3.31 kms-1 in the beginning of 2017 in comparison with 4.16 kms-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.Документ Pulsational activity of the small–amplitude Cepheid Polaris (α UMi) in 2018-2019(Одеський національний університет імені І. І. Мечникова, 2019) Usenko, I. A.; Miroshnichenko, A. S.; Danford, S.; Kovtyukh, Valery V.We present the results of an analysis of 20 spectra of α UMi (Polaris) obtained in September 2018 – January 2019 using 0.81 m 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 km s−1 . The radial velocity amplitude rose to 3.50 km s−1 and actually returned to the previous values of 3.43, 3.31, and 3.81 km s−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 Teff = 6051±22 K shows a growth toward the value found from the 2005 – 2007 observational sets and probably has a tendency toward the Teff growth. The joint TCO and Hermes radial velocity measurements during the last four years show the changes of Polaris’ pulsational amplitude.Документ Refined physical properties of the HD 327083 binary system(Одеський національний університет імені І. І. Мечникова, 2022) Nodyarov, A. S.; Miroshnichenko, A. S.; Khokhlov, S. A.; Zharikov, S. V.; Manset, N.; Usenko, I. A.; Усенко, І. А.HD 327083 is a member of a small group of supergiants exhibiting the B[e] phenomenon. It was found to be a binary system with an early-B and an early-F supergiant components. However the fundamental and orbital parameters of the system were not accurately known. We determined a new set of the system parameters that include the orbital period and the components’ masses using a combination of photometric and spectroscopic data. A new orbital period of 107.7 days was found from both the spectral line positional variations and the visual light curve. Absorption lines of the cool component show a radial velocity semi-amplitude of 48.3 kms-1 , similar to that of emission lines that originate around the hot component. The system shows partial eclipses. We estimated the components’ masses to be nearly equal and close to 6-8 Mq . The masses turned out to be smaller then the evolutionary masses that may be a consequence of a recent mass-transfer.Документ SPECTROSCOPIC INVESTIGATIONS OF CEPHEIDS IN CARINA(Astroprint, 2010-07) Usenko, I. A.; Berdnikov, L. N.; Kravtsov, V. V.; Kniazev, A. Yu.; Chini, R.; Hoffmeister, V. H.; Stahl, O.; Drass, H.Spectroscopic investigations of seven southern CepheidsWWCar, SX Car, UZ Car, UY Car, GX Car, HW Car and YZ Car have been performed. It was founded out six objects have metallicities, close to solar one and their CNO-, odd elements and Mg content indicate that these objects are on the stage after the first dredge-up. CepheidWWCar is an unusual objects because it has noticeable overabundance of [C/H] = +0.3 dex, [N/H] = +0.95 dex, whereas sodium in deficient ([Na/H] = -0.46 dex), and magnesium content is the largest ([Mg/H] = -0.12 dex) in comparison with other objects from this list having close pulsation periods.Документ Spectroscopic investigations of Galactic clusters with associated cepheid variables II NGC 5662 and V CEN(Одеський національний університет імені І. І. Мечникова, 2018) Usenko, I. A.; Kniazev, A. Yu.; Kovtyukh, Valery V.; Mishenina, T. V.; Miroshnichenko, A. S.; Turner, D. G.; Protsyuk, Yu. I.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), vsini, TeS, logg, and [Fe/Hj were determined using model fitting. We have derived the color-excesses, reddenings, and intrinsic colors for these stars to determine their true Tff and log g from comparison to the atmosphere models, especially for hot stars, and to determine their absolute magnitudes. RV and GAIA DR2 2018 parallax/distanee 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 700875 pc, while photometric My 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/Hj = —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.Документ Spectroscopic investigations of Galactic clusters with associated cepheid variables. I. Polaris cluster and UMi(Одеський національний університет імені І. І. Мечникова, 2018) Usenko, I. A.; Miroshnichenko, A. S.; Danford, S.; Kovtyukh, Valery V.; Turner, D. G.; Shulga, O. V.; Protsyuk, Yu. I.We present the results of an analysis of the spectra of nine so called Polaris cluster AFV 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 signi cant di erences for the objects with parallaxes less than 8 mas. The di erences 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.Документ Spectroscopic investigations of galactic clusters with associated Cepheid variables. III. Collinder 394 and BB SGR(Одеський національний університет імені І. І. Мечникова, 2019) Usenko, I. A.; Kniazev, A. Yu.; Katkov, I. Yu.; Kovtyukh, Valery V.; Mishenina, T. V.; Miroshnichenko, A. S.; Turner, D. G.We present the results of a spectroscopic 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), v sin i, Teff, log g, were determined using spectroscopic model fitting and atmosphere models. We have derived the color-excesses, reddenings, and intrinsic colors for these stars using their Teff and log g from comparison 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.Документ Spectroscopic investigations of galactic clusters with associated cepheid variables. IV. Collinder 220 and UW CAR(Одеський національний університет імені І. І. Мечникова, 2020) Usenko, I. A.; Kniazev, A. Yu.; Katkov, I. Yu.; Kovtyukh, Valery V.; Mishenina, T. V.; Miroshnichenko, A. S.; Turner, D. G.We present the results of a spectroscopic 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), v sin i, Te , and log g were determined using spectroscopic model fitting and atmosphere models. We have derived color-excesses, reddenings, and intrinsic colors for these stars using their Te and log g 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 velocity, 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.Документ Spectroscopic investigations of galactic open cluster Collinder 394 – new results(Одеський національний університет імені І. І. Мечникова, 2021) Usenko, I. A.; Kniazev, A. Yu.; Miroshnichenko, A. S.; Danford, S.; Kovtyukh, Valery V.; Mishenina, Tamara V.; Мішеніна, Тамара Василівна; Мишенина, Тамара ВасильевнаConfident main-sequence (MS) members of the Collinder 394 open cluster are perfect objects to check the correctness of their distances, obtained from the GAIA GR2 (2018) catalogue. The differences in the distances to the open cluster Collinder 394, determined by photometry and from the GAIA parallaxes have raised doubts about the correctness of the latter. Therefore we used spectroscopically determined Teff and log gvalues for these stars from Usenko et al. (2019) and tried to solve the inverse problem: determine radii of these stars using the derived distances and calibrations “Teff-radius” for MS stars and compare with similar ones. For this purpose we used the calibrations from Torres et al. (2010), based on the nearest MS eclipsing binaries and compilations for MS stars from Mamajek (2018). As a result, we obtained relationships that connect Teff, log g, radii, masses, and distances for the confident Collinder 394 MS stars. We have confirmed the correctness of the GAIA DR2 (2018) distances for these stars and determined their radii and masses. The latter estimates turned out to be close to those of the evolutionary masses calculated by the PARSEC models.Документ Spectroscopic investigations of Polaris field stars(Одеський національний університет імені І. І. Мечникова, 2023) Usenko, I. A.; Miroshnichenko, A. S.; Danford, S.; Turner, D. G.; Majaess, D. J.; Balam, D. D.We present the results of an analysis of 28 spectra of 18 Polaris field A–G V stars obtained in 2016–2023. Derived radial velocities and Teff along with distances and reddenings from the Gaia DR3 catalog allowed us to calculate radii of the stars and compare them with calibration relationships “Specral type – Luminosity” for MS stars. As a result, radii and distances for 9 stars were found overestimated compred to those determined photometrically. Therefore, the DR3 distances are unreliable and should be revisited. Accordring to our data for these stars and their photometric distances, 15 objects belong to a possible old open cluster that is currently dissolved in the Polarisfieldatadistance∼70–110pc, whiletwoobjectsbelong to the thick disk, and one belongs to a possible another star group located at a distance of 130 pc.Документ Spectroscopic investigations of the polaris ( UMi) system: radial velocity measurements, new orbit, and companion influence for the cepheid polaris aa pulsation activity(Одеський національний університет імені І. І. Мечникова, 2020) Usenko, I. A.; Miroshnichenko, A. S.; Danford, S.; Kovtyukh, Valery V.; Turner, D. G.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 (3.9760.012 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.