Перегляд за Автор "Korotin, S. A."

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  • Ескіз
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    Investigation of diffuse interstellar bands of organic molecules in the spectra of cepheid stars
    (Одеський національний університет імені І. І. Мечникова, 2015) Kashuba, S. V.; Andrievsky, Serhii M.; Chekhonadskikh, F. A.; Korotin, S. A.; Kovtyukh, Valery V.; Luck, R. E.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    We describe an effective method of investigation of the Diffuse Interstellar Bands (DIBs) in the spectra of Cepheid stars. DIBs are believed to originate from the absorption of such carriers as polycyclic aromatic hydrocarbons in the interstellar gaseous clouds located between an observer and the stars whose spectra were recorded. We performed a detailed consideration of the DIB at 6613 A in our sample of spectra for more than 250 stars. The quantitative characteristics of the DIB absorption features will be studied in connection with the interstellar absorption data, and after that, they will be used in the mapping of the Galactic disc.
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    Документ
    The Gaia RVS benchmark stars I. Chemical inventory of the first sample of evolved stars and its Rb NLTE investigation
    (2021) Caffau, E.; Bonifacio, P.; Korotin, S. A.; François, P.; Lallement, R; Matas Pinto, A. M.; Di Matteo, P.; Steffen, M.; Mucciarelli, A.; Katz, D.; Haywood, M.; Chemin, L.; Sartoretti, P.; Sbordone, L.; Andrievsky, Serhii M.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович; Kovtyukh, V. V.; Spite, M.; Spite, F.; Panuzzo, P.; Royer, F.; Thévenin, F.; Ludwig, H.-G.; Marchal, O.; Plum, G.
    Context. The Radial Velocity Spectrometer (RVS) on board the Gaia satellite is not provided with a wavelength calibration lamp. It uses its observations of stars with known radial velocity to derive the dispersion relation. To derive an accurate radial velocity calibration, a precise knowledge of the line spread function (LSF) of the RVS is necessary. Good-quality ground-based observations in the wavelength range of the RVS are highly desired to determine the LSF. Aims. Several radial velocity standard stars are available to the Gaia community. The highest possible number of calibrators will surely allow us to improve the accuracy of the radial velocity. Because the LSF may vary across the focal plane of the RVS, a large number of high-quality spectra for the LSF calibration may allow us to better sample the properties of the focal plane. Methods. We selected a sample of stars to be observed with UVES at the Very Large Telescope, in a setting including the wavelength range of RVS, that are bright enough to allow obtaining high-quality spectra in a short time. We also selected stars that lack chemical investigation in order to increase the sample of bright, close by stars with a complete chemical inventory. Results. We here present the chemical analysis of the first sample of 80 evolved stars. The quality of the spectra is very good, therefore we were able to derive abundances for 20 elements. The metallicity range spanned by the sample is about 1 dex, from slightly metalpoor to solar metallicity.We derived the Rb abundance for all stars and investigated departures from local thermodynamical equilibrium (NLTE) in the formation of its lines. Conclusions. The sample of spectra is of good quality, which is useful for a Gaia radial velocity calibration. The Rb NLTE effects in this stellar parameters range are small but sometimes non-negligible, especially for spectra of this good quality.
  • Ескіз
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    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.
  • Ескіз
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    Zirconium abundances in the Central part of the dSph Fornax galaxy
    (Одеський національний університет імені І. І. Мечникова, 2017) Andrievsky, Serhii M.; Korotin, S. A.; Hill, V.; Zhukova, A. V.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    We derived LTE zirconium abundance in a sample of 81 giant stars in dwarf spheroidal Fornax galaxy. The LTE synthesis was used for this aim. We obtained the lower Zr abundance in Fornax galaxy comparing to the relevant value in the thick/thin disc of the Milky Way. We note that this result may be affected by the NLTE effects that decrease the real zirconium abundance.