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PERIOD VARIATION OF EROS ECLIPSING BINARY SYSTEMS IN THE LARGE MAGELLAN CLOUD
RITTIPRUK, P.,HONG, K.S.,KANG, Y.W. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
We investigated the period variation for 79 eclipsing binary systems using 20 years (1990-2009) of EROS, Macho, and OGLE survey observations. We discovered 9 apsidal motions, 8 mass transfers, 5 period increasing and decreasing systems, 12 light-travel-time effects, 5 eccentric systems and 40 other systems showing no period variations. We select 3 representative eclipsing binary systems; EROS 1052 for apsidal motion, EROS 1056 for mass transfer, and EROS 1037 for the light-travel-time effect. We determine the period variation rate (dP/dt), orbital parameters of the 3rd body (e3, ${\omega}_3$, $f(m_3)$, $P_3$, $T_3$), apsidal motion parameters ($d{\omega}/dt$, U, Ps, Pa, e) and apsidal motion period by analyzing the light curves and O-C diagrams.
Asymmetric Light curves of Contact and Near-Contact Binaries
강영운,Rittipruk, Pakakaew,Kang, Young-Woon 한국천문학회 2012 天文學會報 Vol.37 No.2
We attempt to investigate the main reason of the asymmetrical light curves of contact and near-contact eclipsing binary base on the hypothesis that cool spot was produced on late type star while hot spot was produced from transferred material from their companion star hitting surface. We select 7 eclipsing binary systems which showed asymmetric light curves and mass transfer. Period variation and mass transfer rate were obtained from O-C diagram. Radial velocity curves and light curves of those 7 eclipsing binary system were adopted from available literature in order to obtain the absolute dimension. For four contact eclipsing binary system (AD Phe, EZ Hya, AG Vir and VW Boo), their component stars belonged to spectral type G to K was fitted by cool spot model. While the other two near-contact systems (RT Scl and V1010 Oph) and one contact system (SV Cen) was fitted by cool spot model. The densities of the materials are adopted from stellar model which calculate by stellar structure code. The calculated spot temperature turns out to agree with the photometric solution but there are no correlate between period variation rate and type of spot.
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.
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.
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.
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.