Перегляд за Автор "Sanna, N."

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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
    Systematic investigation of chemical abundances derived using IR spectra obtained with GIANO
    (2019) Caffau, E.; Bonifacio, P.; Oliva, E.; Korotin, S.; Capitanio, L.; Andrievsky, Serhii M.; Collet, R.; Sbordone, L.; Duffau, S.; Sanna, N.; Tozzi, A.; Origlia, L.; Ryde, N.; Ludwig, H.-G.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    ontext. Detailed chemical abundances of Galactic stars are needed in order to improve our knowledge of the formation and evolution of our galaxy, the Milky Way. Aims. We took advantage of the GIANO archive spectra to select a sample of Galactic disc stars in order to derive their chemical inventory and to compare the abundances we derived from these infrared spectra to the chemical pattern derived from optical spectra. Methods. We analysed high-quality spectra of 40 stars observed with GIANO. We derived the stellar parameters from the photometry and the Gaia data-release 2 (DR2) parallax; the chemical abundances were derived with the code MyGIsFOS. For a subsample of stars we compared the chemical pattern derived from the GIANO spectra with the abundances derived from optical spectra. We derived P abundances for all 40 stars, increasing the number of Galactic stars for which phosphorus abundance is known. Results. We could derive abundances of 14 elements, 8 of which are also derived from optical spectra. The comparison of the abun-dances derived from infrared and optical spectra is very good. The chemical pattern of these stars is the one expected for Galactic disc stars and is in agreement with the results from the literature. Conclusions. GIANO is providing the astronomical community with an extremely useful instrument, able to produce spectra with high resolution and a wide wavelength range in the infrared.