Перегляд за Автор "Yushchenko, V. A."

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    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.
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    CHEMICAL COMPOSITION OF PECULIAR STAR HD91375 THE MEMBER OF SIRIUS MOVING GROUP
    (Astroprint, 2010) Yushchenko, V. A.
    We present the results of determinations of the abundances of chemical elements in the atmosphere of hot chemically peculiar star HD91375 - member of Sirius moving group. We used the observations made at 8.2 meter ESO telescope. The abundance pattern of HD91375 is found for the first time, the comparison with the abundances of Sirius A is made. The abundance patterns of Sirius and HD91375 are clearly different. It confirms the possibility of recent accretion event in the Sirius binary system.
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    HIP 13962 - the possible former member of binary system with supernova
    (Одеський національний університет імені І. І. Мечникова, 2016) Yushchenko, V. A.; Yushchenko, A. V.; Gopka, Vera F.; Shavrina, Angelina V.; Kovtyukh, Valery V.; Hong, K. S.; Mkrtichian, D.; A-Thano, N.
    The runaway supergiant star HIP 13962 (spectral type G0Ia) was recently pointed as a possible former binary companion of young pulsar PSR J0826+2637. The spectra of HIP 13962 were obtained in Haute-Provence observatory (France), in Bohuynsan observatory (Korea), and also in NARIT (Thailand) with 1.9, 1.8, and 2.4 meter telescopes respectively. The spectra were obtained in 1995, 2003, 2005, 2014, and 2015. Significant variations of the spectrum are detected. The cores of strong lines show complicated structure, the brightness of the star is variable. The cycles of photometric variations have been changed. We analyzed the spectral observations and present the preliminary chemical composition for elements from iron to lead. The abundance pattern can not be fitted by solar system r- & s-process abundance distribution.
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    PRELIMINARY STUDY OF RED SUPERGIANT RM_1-667 IN THE LARGE MAGELLANIC CLOUD
    (Astroprint, 2012) Gopka, Vera F.; Shavrina, Angelina V.; Vasilyeva, S. V.; Yushchenko, A. V.; Yushchenko, V. A.
    The observed lines of hydrogen and another strong lines in the spectrum of RM_1-667 (red region of spectra, 5900-7100 Å, spectral type is K7 I) are discussed. Analysis of these lines indicates the presence of mass outflow from the star at a significant velocity. Using the iron lines and the model atmospheres of supergiants(Teff = 3750 K – 4300 K) of the Kurucz‘ grid, we obtained the iron abundance lg ε (Fe) = 6.75-7.08, which is equivalent to [Fe/H] equal -0.75 to -0.42.
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    Some statistical picture of magnetic CP stars evolution
    (Astroprint, 2010-07) Gopka, Vera F.; Ulyanov, O. M.; Andrievsky, Serhii M.; Shavrina, Angelina V.; Yushchenko, V. A.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    We discuss some statistical results on the evolution of magnetic CP stars in the framework of the supposition about their binary nature.
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    The abundances of heavy elements in red supergiants of Magellanic Clouds
    (Astroprint, 2013) Gopka, Vera F.; Yushchenko, A. V.; Kovtyukh, Valery V.; Shavrina, Angelina V.; Yushchenko, V. A.; Vasilyeva, S. V.; Pavlenko, Y.; Andrievsky, Serhii M.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    ABSTRACT. The spectra of Magellanic Clouds (MC) supergiants PMMR 23, PMMR 144 and RM 1- 667 with resolving power R=30,000 and signal to noise ratio near 100 obtained at 3.6 meter telescope in Chile were analysed. We present a report on the detailed investigation of MC supergiants, with spesial attention to the thorium abundance in these stars. The abundance patterns of three supergiants show that r-process elements are clearly detected in the atmospheres of investigated stars, but the abundances of s-processes elements can vary from star to star.
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    THE NATURE OF MAGNETIC CHEMICALLY PECULIAR STARS PHENOMENON AND THE ORIGIN OF LITHIUM
    (Astroprint, 2012) Gopka, Vera F.; Shavrina, Angelina V.; Yushchenko, A. V.; Yushchenko, V. A.
    According to the modern theory of the evolution of chemical elements their origin seems understandable for most of the elements, from the lightest up to the heavy ones. For element with atomic number Z=3 (lithium) the situation is following: the physical processes and the possible mechanisms of lithium production in stars of different types and ages remain completely unidentified up to now.
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    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.