ESTUDO ESPECTROSCÓPICO EM ALTA RESOLUÇÃO DAS GIGANTES VERMELHAS DO AGLOMERADO ABERTO NGC 4349

Abstract

ABSTRACT Using a sample of eight high resolution spectra of the red giants in the open cluster NGC 4349, we determined its atmospheric parameters and the chemical abundances of the light elements LiCNO, the refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr e Ni), and the heavy elements produced by the s-process (Y, Zr, La, Ce e Nd) of those stars. We discussed several abundance correlations with parameters as the metallicity, age and the turn-off mass, among others. We calculate also some stellar evolution indicators, as the carbon isotopic ratio or the C/N ratio. Among the analyzed stars, NGC 4349-127 has a sub-stellar object, then we calculate different ratios referred in the exoplanet studies, as the C/O, [Mg/Si] ratios, and the correlation between the abundance ratios [X/Fe] of the refractory elements and their condensation temperature. The previous literature about NGC 4349 focussed on studying the lithium abundance of the host star NGC 4349-127, trying to explain the relation between the evolution of this planetary system, the lithium abundance and the rotation of this star. The results obtained in this study shows that the chemical abundances of the red giants of NGC 4349 are in good agreement with the ones found on the field stars of the thin disk, and in the stars of several open clusters with similar ages and turn-off masses (age of NGC 4349=0.35 Gyr; turn-off mass=3.15 solar masses). We showed that the sub-stellar object is not a relevant reason to produce large discrepancies of the chemical abundances of the host star, considering the trends found in the open cluster NGC 4349, maybe except for a slight increase in the alpha elements abundance of the host star. Regarding the lithium abundance of the host star, we suggest that its value is not out of the trend of the abundances of this element in the red giants of similar open clusters that show a large dispersion of the lithium abundances. We show that the mean abundance value of the s-process elements [s/Fe] of the analyzed stars is consistent with the trend of this abundance with the age, found in field stars and open clusters. It is verified that the abundance of the alpha elements of the non-host red giants of NGC 4349 are in agreement with the ones found in the thin disk stars, regarding the [Y/Mg] ratio. Considering this ratio for the host star NGC 4349-127, we suggest that its overabundance of alpha elements is a consequence of the presence of its sub-stellar object. open clusters; red giant stars; stellar atmospheres; photometric corrections; theoretical isochrones; extrasolar planets; field stars; chemical abundances.