Odesa Astronomical Publications

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https://dspace.onu.edu.ua/handle/123456789/13200

ISSN 1810-4215
eISSN 2786-5215

Журнал «Одеські астрономічні публікації» публікує наукові статі з питань астрономії, астрофізики, космічних досліджень, а також матеріали конференцій, які організовуються й проводяться за участю НДІ «Астрономічна обсерваторія» Одеського національного університету імені І. І. Мечникова.

Повні тексти видання доступні на сайті Наукової бібліотеки ОНУ імені І. І. Мечникова за посиланням:
https://lib.onu.edu.ua/ukrayinska-odessa-astronomical-publications/

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Зараз показуємо 1 - 11 з 11

Actinium abundances in stellar atmospheres
(Одеський національний університет імені І. І. Мечникова, 2021) Yushchenko, V. A.; Gopka, Vera F.; Yushchenko, A.; Shavrina, A.; Pavlenkо, Ja.; Vasil’eva, S.
This paper presents a study of radioactive actinium in the atmospheres of stars located in galaxies with different chemical evolution history – namely, Przybylski's Star (HD 101065) in the Milky Way and the red supergiant PMMR27 in the Small Magellanic Cloud; it also reports the findings of the previous research of the red supergiant RM 1-667 in the Large Magellanic Cloud and the red giant BL138 in the Fornax dwarf spheroidal galaxy. The actinium abundance is close to that of urani um in the atmospheres of certain stars in the Milky Way’s halo and in the atmosphere of Arcturus. The following actinium abundances have been obtained (in a scale of lg N(H) = 12): for the red supergiants PMMR27 and RM 1- 667 lg N(Ac) = -1.7 and lg N(Ac) = -1.3, respectively, and for the red giant BL138 lg N(Ac) = -1.6. The actinium abundance in the atmosphere of Przybylski's Star (HD 101065) is lg N(Ac) = `0.94±0.09, which is more than two orders of magnitude higher than those in the atmospheres of the other studied stars.
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.
Hafnium abundances in fgk dwarf of galactic disk
(Одеський національний університет імені І. І. Мечникова, 2018) Gorbanova, Tetiana I.; Mishenina, Tamara V.; Горбаньова, Тетяна Іванівна; Мішеніна, Тамара Василівна
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.
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.
Molybdenum abundance in some open clusters
(Одеський національний університет імені І. І. Мечникова, 2018) Shereta, E. P.; Carraro, G.; Gorbanova, Tetiana I.; Mishenina, Tamara V.; Шерета, Е. П.; Карраро, Ж.; Горбаньова, Тетяна Іванівна; Мішеніна, Тамара Василівна
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.
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.
Molybdenum and ruthenium in the Galaxy
(Одеський національний університет імені І. І. Мечникова, 2018) Mishenina, Tamara V.; Gorbanova, Tetiana I.; Мішеніна, Тамара Василівна; Горбаньова, Тетяна Іванівна
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.
Status refinement of metal-poor star HD 6268
(Одеський національний університет імені І. І. Мечникова, 2018) Mishenina, Tamara V.; Usenko, Igor O.; Kniazev, A. Yu.; Kovtyukh, Valery V.; Мішеніна, Тамара Василівна; Усенко, Ігор Олександрович; Князев, А. Ю.; Ковтюх, Валерій Володимирович
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.
THE PLANETARY HOST RED GIANT HD47536 - CHEMICAL COMPOSITION AND SIGNS OF ACCRETION
(Astroprint, 2013) Yushchenko, A. V.; Rittipruk, P.; Yushchenko, V. A.; Kang, Y.-W.
The spectra of HD47536 with resolving power R=30,000 and signal to noise ratio near 100 was obtained at 1.5 meter SMART telescope of CTIO, Chile. The analysis of chemical composition allowed to find the abundances of 33 chemical elements including thorium. The star belongs to halo or intermediate population, it’s metallicity is [Fe/H]=-0.58 0.11, the r- and s-processes elements are overabundant with respect to iron. The overabundance of thorium with respect to iron is +0.72 dex. The abundance pattern exhibits the clear signs of accretion. The star is a host of two planets, that is why it can be the result of the accretion in planetary system or the accretion of interstellar gas. The signs of accretion are clearly detected and prevent the determination of stellar age.
Three giants – members of The Open cluster M 67
(Одеський національний університет імені І. І. Мечникова, 2017) Mishenina, T. V.; Klochkova, V. G.; Panchuk, V.; Basak, N. Yu.; Kovtyukh, Valery V.; Korotin, S. A.; Velichko, A.
We determined the atmospheric parameters and chemical composition of the three giants, which are members of the open cluster M 67. The high resolution spectra (R = 60 000) were obtained with the echelle spectrograph NES mounted on the 6-meter telescope of the SAO RAS Obtained variations in Na and Zr abundances are within the determination errors. The Li abundance suggest a depletion of Li in the course of stellar evolution. For studied giants, the iron abundances derived from the neutral and ionized iron lines have not shown any significant discrepancies. The [Ba/Fe] values are close to the solar ones.
TYC5594-576-1: R-process enrichment metal-poor star
(Одеський національний університет імені І. І. Мечникова, 2021) Mishenina, Tamara V.; Usenko, I. A.; Kniazev, A. Yu.; Kovtyukh, Valery V.; Мішеніна, Тамара Василівна; Мишенина, Тамара Васильевна
Atmospheric parameters and elemental abundances of metal-poor Population II star TYC5594- 576-1 ([Fe/H] = –2.8) have been studied, including the elements of neutron (n-) capture processes, as an im portant part of the enrichment sources of early Galaxy. Na, Mg, Al, Co, Sr, Y, Zr, Mo, Ba, La, Ce, Pr, Sm, Eu, Gd, Dy, Os, and Th abundances were determined using the synthetic spectrum method, taken into account the hyperfine structure (HFS) for the Ba II, La II and Eu II lines. The abundances of Si, Ca, Sc, N were determined based on the equivalent widths of their lines. The carbon abundance was obtained by the molecular synthesis fitting for the CH region of 4300-4330 ÅÅ. For the abundances determinations of C, Na, Mg, Al, Ba, and Th the NLTE corrections have been applied. We have determined the abundances of several n capture elements for the first time and found that the be haviour of these elements abundances shows a significant trend with increasing atomic number. The elements ratios of [Eu/Fe] = 1.85, [Ba/Eu] = –1.24, [Sr/Ba] = –1.04 con firm the status of TYC5594-576-1 as a r-process enrich ment star, with lower strontium [Sr/Fe] = –0.33 and higher thorium [Th/Fe] = 1.28 abundances. The obtained europium and thorium excesses testifies to the early en richment of the Galaxy by the r-process elements as a result of the merger of neutron stars or black holes. The car bon abundance confirms the effect of canonical additional mixing in this star.

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