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Yushchenko, Alexander,Kim, Seunghyun,Jeong, Yeuncheol,Demessinova, Aizat,Yushchenko, Volodymyr,Doikov, Dmytry,Gopka, Vira,Jeong, Kyung Sook,Rittipruk, Pakakaew The Korean Space Science Society 2021 Journal of Astronomy and Space Sciences Vol.38 No.3
The dependencies of the chemical element abundances in stellar atmospheres with respect to solar abundances on the second ionization potentials of the same elements were investigated using the published stellar abundance patterns for 1,149 G and K giants in the Local Region of the Galaxy. The correlations between the relative abundances of chemical elements and their second ionization potentials were calculated for groups of stars with effective temperatures between 3,764 and 7,725 K. Correlations were identified for chemical elements with second ionization potentials of 12.5 eV to 20 eV and for elements with second ionization potentials higher than 20 eV. For the first group of elements, the correlation coefficients were positive for stars with effective temperatures lower than 5,300 K and negative for stars with effective temperatures from 5,300 K to 7,725 K. The results of this study and the comparison with earlier results for hotter stars confirm the variations in these correlations with the effective temperature. A possible explanation for the observed effects is the accretion of hydrogen and helium atoms from the interstellar medium.
Yushchenko, Alexander,Kim, Seunghyun,Jeong, Yeuncheol,Demessinova, Aizat,Yushchenko, Volodymyr,Doikov, Dmytry,Gopka, Vira,Jeong, Kyung Sook,Rittipruk, Pakakaew The Korean Space Science Society 2021 Journal of astronomy and space sciences Vol.38 No.3
The dependencies of the chemical element abundances in stellar atmospheres with respect to solar abundances on the second ionization potentials of the same elements were investigated using the published stellar abundance patterns for 1,149 G and K giants in the Local Region of the Galaxy. The correlations between the relative abundances of chemical elements and their second ionization potentials were calculated for groups of stars with effective temperatures between 3,764 and 7,725 K. Correlations were identified for chemical elements with second ionization potentials of 12.5 eV to 20 eV and for elements with second ionization potentials higher than 20 eV. For the first group of elements, the correlation coefficients were positive for stars with effective temperatures lower than 5,300 K and negative for stars with effective temperatures from 5,300 K to 7,725 K. The results of this study and the comparison with earlier results for hotter stars confirm the variations in these correlations with the effective temperature. A possible explanation for the observed effects is the accretion of hydrogen and helium atoms from the interstellar medium.
Yushchenko, Alexander,Doikov, Dmytry,Andrievsky, Sergei,Jeong, Yeuncheol,Yushchenko, Volodymyr,Rittipruk, Pakakaew,Kovtyukh, Valery,Demessinova, Aizat,Gopka, Vira,Raikov, Alexander,Jeong, Kyung Sook The Korean Space Science Society 2022 Journal of astronomy and space sciences Vol.39 No.4
We investigated the chemical composition of the planetary host halo star HD47536 via high-resolution spectral observations recorded using a 1.5 meter Cerro Tololo Inter-American Observatory (CTIO) telescope (Chile). Furthermore, we determined the abundances of 38 chemical elements. Both light and heavy elements were overabundant compared to the iron group elements. The abundance pattern of HD47536 was similar to that of halo-type stars, with an enrichment of heavy elements. We analyzed the relationships between the relative abundances of chemical elements and their second ionization potentials and condensation temperatures. We demonstrated that the interplay of charge-exchange reactions owing to the accretion of interstellar matter and the gas-dust separation mechanism can influence the initial abundances and can be used to qualitatively explain the abundance patterns in the atmosphere of HD47536.
Constant Acceleration in Fractal Structures with Fractal Dimension D = 2
Alexander Yushchenko,Yeuncheol Jeong,Volodymyr Yushchenko,Aizat Demessinova,Kyung Sook Jeong The Korean Space Science Society 2023 Journal of Astronomy and Space Sciences Vol.40 No.1
An unexplained acceleration on the order of 10<sup>-8</sup> cm s<sup>-2</sup>, which is close to cH, where c is the speed of light and H is the Hubble constant, is detected in gravitationally bound systems of different scales, from the solar system to clusters of galaxies. We found that any test body located inside a fractal structure with fractal dimension D = 2 experiences acceleration of the same order and confirmed the previous work that photons propagating through this structure decrease the frequency owing to gravitational redshift. The acceleration can be directed against the movement of the test body. The fractal distribution of the matter should be at scales of at least hundreds of megaparsecs to a few gigaparsecs for the existence of this acceleration.
Alexander Yushchenko,Dmytry Doikov,Sergei Andrievsky,Yeuncheol Jeong,Volodymyr Yushchenko,Pakakaew Rittipruk,Valery Kovtyukh,Aizat Demessinova,Vira Gopka,Alexander Raikov,Kyung Sook Jeong 한국우주과학회 2022 Journal of Astronomy and Space Sciences Vol.39 No.4
We investigated the chemical composition of the planetary host halo star HD47536 via high-resolution spectral observations recorded using a 1.5 meter Cerro Tololo Inter-American Observatory (CTIO) telescope (Chile). Furthermore, we determined the abundances of 38 chemical elements. Both light and heavy elements were overabundant compared to the iron group elements. The abundance pattern of HD47536 was similar to that of halo-type stars, with an enrichment of heavy elements. We analyzed the relationships between the relative abundances of chemical elements and their second ionization potentials and condensation temperatures. We demonstrated that the interplay of charge-exchange reactions owing to the accretion of interstellar matter and the gas-dust separation mechanism can influence the initial abundances and can be used to qualitatively explain the abundance patterns in the atmosphere of HD47536.
Alexander V. Yushchenko,Chulhee Kim,Yeuncheol Jeong,Dmytry N. Doikov,Volodymyr A. Yushchenko,Sergii V. Khrapatyi,Aizat Demessinova 한국우주과학회 2020 Journal of Astronomy and Space Sciences Vol.37 No.3
High resolution spectroscopic observation of V1719 Cyg were made at 1.8 meter telescope of Bohyunsan Optical Astronomy observatory in Korea. Spectral resolving power was R=45,000, signal to noise ratio S/N>100. The abundances of 28 chemical elements from carbon to dysprosium were found with the spectrum synthesis method. The abundances of oxygen, titanium, vanadium and elements with Z>30 are overabundant by 0.2–0.9 dex with respect to the solar values. Correlations of derived abundances with condensation temperatures and second ionization potentials of these elements are discussed. The possible influence of accretion from interstellar environment is not so strong as for ρ Pup and other stars with similar temperatures. The signs of accretion are absent. The comparison of chemical composition with solar system r- & s-process abundance patterns shows the enhancement of the photosphere by s-process elements.
Chemical Composition of RM_1-390 - Large Magellanic Cloud Red Supergiant
Alexander V. Yushchenko,정연철,Vira F. Gopka,Svetlana V. Vasil’eva,Sergey M. Andrievsky,Volodymyr O. Yushchenko 한국우주과학회 2017 Journal of Astronomy and Space Sciences Vol.34 No.3
A high resolution spectroscopic observation of the red supergiant star RM_1-390 in the Large Magellanic Cloud was made from a 3.6 m telescope at the European Southern Observatory. Spectral resolving power was R=20,000, with a signal-to-noise ratio S/N > 100. We found the atmospheric parameters of RM_1-390 to be as follows: the effective temperature Teff = 4,250 ± 50 K, the surface gravity log g = 0.16 ± 0.1, the microturbulent velocity vmicro = 2.5 km/s, the macroturbulence velocity vmacro = 9 km/s and the iron abundance [Fe/H] = -0.73 ± 0.11. The abundances of 18 chemical elements from silicon to thorium in the atmosphere of RM_1-390 were found using the spectrum synthesis method. The relative deficiencies of all elements are close to that of iron. The fit of abundance pattern by the solar system distribution of r- and s-element isotopes shows the importance of the s-process. The plot of relative abundances as a function of second ionization potentials of corresponding chemical elements allows us to find a possibility of convective energy transport in the photosphere of RM_1-390.
Chemical Composition of RR Lyn – an Eclipsing Binary System with Am and λ Boo Type Components
정연철,Alexander V. Yushchenko,Dmytry N. Doikov,Vira F. Gopka,Volodymyr O. Yushchenko 한국우주과학회 2017 Journal of Astronomy and Space Sciences Vol.34 No.2
High-resolution spectroscopic observations of the eclipsing binary system RR Lyn were made using the 1.8 m telescope at the Bohuynsan Optical Astronomical Observatory in Korea. The spectral resolving power was R = 82,000, with a signal to noise ratio of S/N > 150. We found the effective temperatures and surface gravities of the primary and secondary components to be equal to Teff = 7,920 & 7,210 K and log(g) = 3.80 & 4.16, respectively. The abundances of 34 and 17 different chemical elements were found in the atmospheric components. Correlations between the derived abundances with condensation temperatures and the second ionization potentials of these elements are discussed. The primary component is a typical metallic line star with the abundances of light and iron group elements close to solar values, while elements with atomic numbers Z > 30 are overabundant by 0.5–1.5 dex with respect to solar values. The secondary component is a λ Boo type star. In this type of stars, CNO abundances are close to solar values, while the abundance pattern shows a negative correlation with condensation temperatures.
The Barium Star HD204075: Iron Abundance and the Absence of Evidence for Accretion
Yeuncheol Jeong,Alexander Yushchenko,Vira Gopka,Volodymyr Yushchenko,Pakakaew Rittipruk,Kyung Sook Jeong,Aizat Demessinova 한국우주과학회 2019 Journal of Astronomy and Space Sciences Vol.36 No.3
Spectroscopic observations of barium star ζ Capricornus (HD204075) obtained at the 8.2 m telescope of the European Southern Observatory, with a spectral resolving power R = 80,000 and signal to noise ratio greater than 300, were used to refine the atmospheric parameters. We found new values for effective temperature (Teff = 5,300 ± 50 K), surface gravity (log g = 1.82 ±0.15), micro-turbulent velocity (vmicro = 2.52 ± 0.10 km/s), and iron abundance (log N (Fe) = 7.32 ± 0.06). Previously published abundances of chemical elements in the atmosphere of HD204075 were analyzed and no correlations of these abundances with the second ionization potentials of these elements were found. This excludes the possible influence of accretion of hydrogen and helium atoms from the interstellar or circumstellar environment to the atmosphere of this star. The accretion of nuclear processed matter from the evolved binary companion was primary cause of the abundance anomalies. The young age of HD204075 allows an estimation of the time-scale for the creation of the abundance anomalies arising from accretion of interstellar hydrogen and helium as is the case of stars with low magnetic fields; which we estimate should exceed 10^8 years.