Estudo espectroscópico em aglomerados abertos: NGC 2447 e NGC 6664

Abstract

In this work we analyzed, using high-resolution spectroscopy, a sample of 12 single and 4 spectroscopic binary red giant stars of the open cluster NGC 2447 and another sample made up of 4 red giants stars from the open cluster NGC 6664, where 3 of them are binaries and the other is a single star. For the single giant stars of NGC 2447 we obtained their atmospheric parameters and chemical abundances for Li, C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, Nd, Ba, Eu and the isotopic ratio 12C/13C. Rotational and radial velocities were obtained for the stars of this cluster. We employed local thermodynamic equilibrium model atmospheres and the spectral analysis code IRAF. The abundances of the light elements (lithium, carbon, nitrogen and oxigen) and the rotational velocities were derived using spectral synthesis technique. The abundances derived for the other elements followed the equivalent width method with the code MOOG. For the giant stars from the cluster NGC 6664 we obtained their atmospheric parameters and chemical abundances for the elements of the s-process, meaning Y, Zr, La, Ce and Nd. This determination has the aim to caracterize these objects as possible barium stars. We determined the radial velocities of these objects as well. Due to the lack of data in the literature the comparison with published works could not be done. We obtained a mean metallicity of [Fe/H] = -0.17+/-0.05 for NGC 2447 and [Fe/H] = -0.20+/-0.09 for NGC 6664. We found that the abundances of the stars from NGC 2447 are similar to other field giants and/or giants of open clusters. Our abundance analysis of NGC 6664 found an object that could eventually be considered as a barium star. The stars NGC 2447-26, 38 and 42 are yellow-stragglers, of which the primary is a giant star and the secondary is probably an A-type star. Our work confirms the binary nature of NGC 2447-38. The binary nature of NGC 2447-38 and all of the results for the cluster NGC 6664 have not been published in the literature.