Статті та доповіді ФМФІТ

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https://dspace.onu.edu.ua/handle/123456789/1928

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Перегляд Статті та доповіді ФМФІТ за Автор "Andrievsky, Serhii M."

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  • Ескіз
    Документ
    GIANO Y-band spectroscopy of dwarf stars: Phosphorus, sulphur, and strontium abundances
    (2016) Caffau, E.; Andrievsky, Serhii M.; Korotin, Sergei A.; Origlia, L.; Oliva, E.; Sanna, N.; Ludwig, H.-G.; Bonifacio, P.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    Context. In recent years a number of poorly studied chemical elements, such as phosphorus, sulphur, and strontium, have received special attention as important tracers of the Galactic chemical evolution. Aims. By exploiting the capabilities of the infrared echelle spectrograph GIANO mounted at the Telescopio Nazionale Galileo, we acquired high resolution spectra of four Galactic dwarf stars spanning the metallicity range between about one-third and twice the solar value. We performed a detailed feasibility study about the effectiveness of the P, S, and Sr line diagnostics in the Y band between 1.03 and 1.10 μm. Methods. Accurate chemical abundances have been derived using one-dimensional model atmospheres computed in local thermodynamic equilibrium (LTE).We computed the line formation assuming LTE for P, while we performed non-LTE analysis to derive S and Sr abundances. Results. We were able to derive phosphorus abundance for three stars and an upper limit for one star, while we obtained the abundance of sulphur and strontium for all of the stars. We find [P/Fe] and [S/Fe] abundance ratios consistent with solar-scaled or slightly depleted values, while the [Sr/Fe] abundance ratios are more scattered (by ±0.2 dex) around the solar-scaled value. This is fully consistent with previous studies using both optical and infrared spectroscopy. Conclusions. We verified that high-resolution, Y-band spectroscopy as provided by GIANO is a powerful tool to study the chemical evolution of P, S, and Sr in dwarf stars.
  • Ескіз
    Документ
    Photometric and spectroscopic analysis of Comet 29P/Schwassmann-Wachmann 1 activity
    (2016-02) Ivanova, Oleksandra V.; Luk'yanyk, Igor V.; Kiselev, Nikolay N.; Afanasiev, Viktor L.; Picazzio, Enos; Cavichia, Oscar; Almeida, Amaury A. de; Andrievsky, Serhii M.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    We carried out photometric and spectroscopic observations of comet 29P/Schwassmann-Wachmann 1 at the 6-m BTA telescope (SAO RAS, Russia) and the 1.6-m telescope of the National Laboratory for Astrophysics (LNA, Brazil) on February 20, 2012, and on May 31, 2011, respectively. The spectra revealed the presence of CO+ and N2+ emissions in the cometary coma at a distance of 5.25 AU from the Sun. The ratio [N2+]/[CO+] within the projected slit is 0.013. The images obtained through BVR filters showed a bright, dust coma, indicating a high level of activity. We estimated a colour index and a colour excess for the comet. The parameter Afρ, which is used as an indicator of a cometary activity, was measured to be 2584±50 cm in the reference optical aperture of ρ=104 km. The dust production constituted 33 kg/s and 9.3·103 kg/s, it was obtained using different methods. We also investigated the morphology of the comet using image enhancement techniques and found two jets in the coma.