Перегляд за Автор "Mishenina, T. V."
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Документ ANALYSIS OF THE PARAMETERS AND ABUNDANCE OF N-CAPTURE ELEMENTS FOR FOUR STARS WITH DIFFERENT METALLICITY(Astroprint, 2013) Basak, N. Yu.; Mishenina, T. V.ABSTRACT. Based on the spectra obtained with echelle spectrograph SOPHIE (1.93 m telescope, OHP, France) and the selection of lines (Basak & Mishenina, 2012). we have redefined the parameters and have determined the abundances of the elements produced in the process of neutron captures for stars HD 6582, HD19445, HD 84937, HD170153. Obtained abundance of Y, Zr, La, Ce, P, Nd, Sm, and Gd,shows the solar scaled abundance distribution.Документ Chemical imprints in atmospheric abundances in planet- hosting stars(Одеський національний університет імені І. І. Мечникова, 2019) Mishenina, T. V.; Basak, N. Yu.; Kovtyukh, Valery V.; Мишенина, Т. В.; Басак, Н. Ю.; Ковтюх, Валерій В.We examined 12 planet-hosting stars based on homogeneous spectral data (obtained with the SOPHIE echelle spectrograph with R = 75,000 at the OHP, France) and using uniform techniques for determination of parameters and abundances of a series of elements (Li, C, Na, Mg, Al, S, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Ba, La, Ce, Pr, Nd, Sm and Eu). For our set of stars with detected massive planets, we have found [Fe/H] ranging from --0.3 to 0.4 dex. There is the only star for which the lithium content has been reliably shown to be lower than predicted values. Average C/O ratio (0.52±0.08) is slightly lower than the solar one (0.54), and C/O ratios tend to correlate with the planetary mass. Magnesium follows the trend in Galactic chemical evolution exhibiting a dependence on the planetary mass. Manganese and barium are both slightly overabundant.Документ EU ABUNDANCES IN ACTIVE AND NON-ACTIVE STARS(Astroprint, 2010-07) Gorbaneva, Tatyana I.; Mishenina, T. V.Eu abundances have been determined for stars observed at high resolution, high signal to noise ratio with the ELODIE spectrograph at the 1.93-m telescope of the Observatoire de Haute Provence(France). Among them more than 30 stars are active stars with a fraction of BY Dra and RS CVn type stars for which spectral pecularities were investigated. For all stars fundamental parameters were determined earlier. We nd the mean abundances of the majority of elements in active and non-active stars. Active and non active cool dwarfs show similar dependencies of elemental ratios vs [Fe/H].Документ Hafnium abundances in fgk dwarf of galactic disk(Одеський національний університет імені І. І. Мечникова, 2018) Gorbaneva, Tatyana I.; Mishenina, T. V.; Горбаньова, Тетяна І.; Мишенина, Т. В.In this work we present new observational data for hafnium (72). Hf is an important element that is between the lightest rare-earth elements (e.g., La, Z = 57) with elements of the third r-process peak (Os, Ir, Pt, Z =76-78). Hafnium is the heaviest (Z = 72) stable element represented by low-excitation (<1:5 eV) ionized lines in the spectra of the cool stars (Lawler et al., 2007). This element is important as a stable reference element for nucleocosmochronometry, and also to study of the sources of its production and enrichment with n (neutron)-capture elements of Galactic disc. We provide the analysis of the spectra of 126 FGK dwarfs in metallicity range from −1.0 < [Fe/H] < +0.3 that were taken from our starting sample of 276 stars (Mishenina et al. 2013). The observed stars belong to the substructures of the Galaxy disc. The observations were conducted using the 1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle type spectrographs ELODIE and SOPHIE. The results are based on analyses of spectra that have a typical S/N ~ 100-300 and a resolution of 42 000 (ELODIE) and 75 000(SOPHIE). The hafnium abundance was derived by comparing the observed and synthetic spectra in the region of two Hf II line (λ4080.437 Å and λ4093.155 Å), making use of the LTE approximation. The obtained hafnium abundance decrease with increasing metallicity in both discs, and have a big scatter at all metallicities. The dependence of our Hf abundance on metallicity and their comparison with those of other authors is presented. It corresponds to typical behavior of the elements behind the iron peak, the elements formed in the processes of neutron capture. The sources of the Hf enrichment of Galactic disc are considered.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 IN COMMEMORATION OF THE 75TH BIRTHDAY ANNIVERSARY OF NIKOLAY S. KOMAROV(Astroprint, 2013) Mishenina, T. V.; Dragunova, A. V.Nikolay Sergeyevich Komarov (16.06.1938–03.08.2003) was born in Sestroretsk town in Leningrad region (USSR) in the family of a naval officer. After the World War II his family moved to Odessa. In 1955, Nikolay graduated from a high school and entered the Department of Mathematics of the Faculty of Mathematical and Physical Sciences at Odessa State University. The launch of the first artificial Earth’s satellite aroused his interest in outer space, and he transferred to the Department of Physics of the faculty to specialise in astronomy. During 1955-1960, Nikolay Komarov was a leader among other students in Odessa as he had the largest number of artificial satellite observations. He was very enthusiastic about spectroscopy as far back as he was a student and made the meteor spectra the subject of his graduation Master’s paper.Документ LINES SELECTION TO DETERMINE THE CHEMICAL COMPOSITION OF STARS IN THE RANGE -3 ≤ [FE/H] ≤ -0.7(Astroprint, 2012) Basak, N. Yu.; Mishenina, T. V.ABSTRACT. Using the spectra obtained with echelle spectrograph SOPHIE (1.93 m telescope, OHP, France)and the data from about 20 papers of various authors, we have compiled a list for around four thousand lines of different chemical elements. Based on the spectra of the Sun and stars and also synthetic spectrum calculations in different ranges of metallicity, we selected 300 unblended lines of FeI, FeII and 200 lines of YII, ZrI, ZrII, LaII,CeII, PrII, NdII, SmII, GdII, that are recommended for thestudy of the chemical composition.Документ Molybdenum abundance in some open clusters(Одеський національний університет імені І. І. Мечникова, 2018) Shereta, E. P.; Carraro, G.; Gorbaneva, Tatyana I.; Mishenina, T. V.; Шерета, Е. П.; Карраро, Ж.; Горбаньова, Тетяна І.; Мишенина, Т. В.This paper presents the results of determination of the molybdenum abundances in 13 G, K type stars in the open clusters NGC 2477 and NGC 2506. The abundances of molybdenum were determined using stellar atmosphere models by Castelli & Kurucz (2004), as well as a modified STARSP LTE spectral synthesis code (Tsymbal, 1996). For the used Mo I lines 5506 and 5533 Å the oscillator strengths log gf were adopted from the latest version of the VALD database dated 2016 (Kupka et al., 1999). The high resolution spectra were obtained with a VLT telescope at the European Southern observatory (ESO, Chile). We used atmospheric parameters of the investigated stars which we had obtained earlier. We have found out that the molybdenum abundances depend on metallicity [Fe/H] in giants of NGC 2506 and NGC 2477. For the stars in NGC 2506, molybdenum is slightly overabundant as compared to the solar abundance; such an overabundance is slightly higher in the stars of the second investigated cluster NGC 2477. Further investigation of the Mo abundance in larger number of open clusters is required to draw reliable conclusions.Документ Molybdenum and Ruthenium abundances in Cool stars of the Galactic DISC(Одеський національний університет імені І. І. Мечникова, 2017) Gorbaneva, Tatyana I.; Mishenina, T. V.We revise the molybdenum and ruthenium abundances in FGK stars with metallicities ranging from −1.0 < [Fe/H] < +0.3. The observed stars belong to the substructures of the Galaxy. The observations were conducted using the 1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle type spectrographs ELODIE and SOPHIE. The results are based on analyses of spectra that have a typical S/N ~ 100-300 and a resolution of 42 000. These estimates were obtained using synthetic spectra computed with LTE model atmosphere.Документ Molybdenum and ruthenium in the Galaxy(Одеський національний університет імені І. І. Мечникова, 2018) Mishenina, T. V.; Gorbaneva, Tatyana I.; Мишенина, Т. В.; Горбаньова, Тетяна І.We present a brief overview of the molybdenum and ruthenium present-day nucleosynthesis calculations and abundance determinations in stars belonging to different substructures (populations) in the Galaxy. The following sources of Mo, Ru production were considered: the Asymptotic Giant Branch (AGB) stars of different masses (main s-process), massive stars (weak s-process), neutrino-induced winds from the core-collapse supernova CCSNe (weak r-process), merging of neutron stars (main rprocess). Many production sites of the p-nuclei have been proposed: the Type II and Ia supernovae (at the presupernova phase, during and after the supernova explosion), the rp-process in neutrino-driven winds, the high-entropy wind (HEW), the νp-process; inside in a supercritical accretion disk (SSAD), in the He-accreting CO white dwarfs of sub-Chandrasekhar mass, and in the carbon deflagration model for Type Ia. We also emphasize on some additional processes such as the i- process in rapidly accreting white dwarfs (RAWDs), the lighter element primary process LEPP as well as another formation channel, namely the charged-particle process (r- process). The contribution to the solar abundance of neutron capture elements and the Galactic Chemical Evolution (GCE) models for n-capture elements were considered. The Mo and Ru observations in metal-poor stars, Ba stars, globular clusters, meteoritic matter (presolar grains) as well as our new Mo and Ru determinations in Galactic disc are presented. Having analysed our date in the near solar metallicities we found out that there are different sources contributing to the Mo and Ru abundances, and that the main s-process contribution to the Mo and Ru abundances is lower than to the predominant s-element (Y, Zr and Ba) solar abundances. By comparing the behavior of Mo and Ru in the wide range of [Fe/H] with GCE models one can see that the theoretical description of the galactic behavior of Mo not depicts sufficient and we are faced with the underproduction of molybdenum in the sources and in processes that used at the GCE creation. Additional sources may be the p-process (SN Ia and/or SN II), νp-process (massive stars) or several more exotic processes.Документ n-CAPTURE ELEMENTAL ABUNDANCES IN ACTIVE AND NON-ACTIVE STARS(Astroprint, 2010-07) Basak, N. Yu.; Mishenina, T. V.; Soubiran, C.; Kovtyukh, Valery V.; Belik, S. I.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.Документ Nuclear magics at magnetorotational supernova explosion(Одеський національний університет імені І. І. Мечникова, 2015) Kondratyev, V. N.; Korovina, Yu. V.; Mishenina, T. V.Nucleosynthesis at magnetorotational supernova explosion is considered by employing arguments of nuclear statistical equilibrium. Effects of ultra-strong nuclear magnetization are demonstrated to enhance the portion of titanium product. The relation to an excess of 44Ti revealed from the Integral mission data and galactic chemical evolution is discussed.Документ Nucleosynthesis at magnetorotational supernova explosion and galactic chemical evolution(Одеський національний університет імені І. І. Мечникова, 2016) Kondratyev, V. N.; Mishenina, T. V.Synthesis of chemical elements is investigated at conditions of magnetorotational instabilities in astrophysical plasma at supernova explosion. Effects of ultra-strong nuclear magnetization are demonstrated to enhance the portion of titanium product. The relation to an excess of 44Ti revealed from the Integral mission data and galactic chemical evolution is discussed.Документ OPEN CLUSTERS AND FIELD CEPHEIDS IN THE GALACTIC DISK – CONTRADICTIONS IN PROPERTIES(Astroprint, 2013) Marsakov, V. A.; Koval, B. B.; Gozha, M. L.; Kovtyukh, B. B.; Mishenina, T. V.ABSTRACT. 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.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. 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 Status refinement of metal-poor star HD 6268(Одеський національний університет імені І. І. Мечникова, 2018) Mishenina, T. V.; Usenko, I. A.; Kniazev, A. Yu.; Kovtyukh, Valery V.; Мишенина, Т. В.; Усенко, І. А.; Князев, А. Ю.; Ковтюх, Валерій В.Metal-poor stars in the Galaxy enable observations of the light and neutron-capture (n-capture) elements produced by their progenitors and deduction of the characteristics of the early Galaxy from the elemental abundances in these stars. Stars with deficiency of metals ([Fe/H] < –2) vary significantly in their chemical composition, in particular, in their content of CNO elements, as well as the iron-peak and n-capture elements. A detailed study of the elemental abundances in these stars makes it possible to test experimental models of stellar evolution, nucleosynthesis, homogeneity (the degree of mixing) of interstellar matter, etc., at low metallicity in the Galaxy. The metal-poor star HD 6268 with [Fe/H] close to – 2.5 and low carbon abundance was selected as a target one for this study. The spectral material was collected using the Southern African Large Telescope (SALT) fibre-fed echelle-spectrograph HRS in the medium resolution mode (R~31000-41000) with a high S/N ratio near 100-200 within the range from 3900 to 8700 ÅÅ. The atmospheric stellar parameters and abundances of 30 chemical elements in the metal-poor star HD 6268 were determined under the LTE approximation using the atmosphere models by Kurucz & Castelli (2003), as well as the equivalent widths EWs and WIDH9 code developed by Kurucz. The abundances of C, Na, Mg, K, Ba, La, Ce, Pr, Sm and Eu were obtained by the synthetic spectrum method factoring in the hyperfine structure (HFS) for the Eu II line 4129 A. The carbon abundance was determined by the molecular synthesis fitting in the region of CH (4300-4330 ÅÅ). For the abundances of Na, Mg, K and Ba, we applied the NLTE corrections. As a result, we found out that the abundances of C and N confirm their changes associated with canonical extra mixing proposed by Denissenkov & Pinsonneault (2008). The Na-O correlation is open to question unlike the Na-Si correlation which is likely to exist. The Al-Mg and Al-Na correlations are consistent with the data obtained for the field giants with [C/Fe] < –0.5 (Roederer et al., 2014). According to the distribution of elements depending on their atomic numbers in the atmosphere of HD 6268, it is a metal-poor main r-process enriched star.Документ Strontium abundances in cool dwarf stars of galactic thin and thick disks(Одеський національний університет імені І. І. Мечникова, 2016) Gorbaneva, Tatyana I.; Mishenina, T. V.We revise the strontium abundances in FGK stars with metallicities ranging from −1.0 < [Fe/H] < +0.3. The observed stars belong to the substructures of the Galaxy thick and thin discs. The observations were conducted using the 1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle type spectrographs ELODIE and SOPHIE. The values of the Sr abundance were obtained using synthetic spectra using LTE model atmosphere. The comparison of our data with models of chemical evolution was made.Документ Strontium abundances in cool dwarf stars of galactic thin and thick disks(Одеський національний університет імені І. І. Мечникова, 2016) Gorbaneva, Tatyana I.; Mishenina, T. V.We revise the strontium abundances in FGK stars with metallicities ranging from −1.0 < [Fe/H] < +0.3. The observed stars belong to the substructures of the Galaxy thick and thin discs. The observations were conducted using the 1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle type spectrographs ELODIE and SOPHIE. The values of the Sr abundance were obtained using synthetic spectra using LTE model atmosphere. The comparison of our data with models of chemical evolution was made.