High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements

Abstract

The main atmospheric parameters and abundances of the iron-group elements (vanadium, chromium, iron, cobalt and nickel) are determined for 62 red giant 'clump' stars revealed in the Galactic field by the Hipparcos orbiting observatory. The stars form a homogeneous sample with the mean value of temperature T_(eff)= 4750 ± 160 K, of surface gravity log g= 2.41 ± 0.26 and the mean value of metallicity [Fe/H]=−0.04 ± 0.15 dex. A Gaussian fit to the [Fe/H] distribution produces the mean 〈[Fe/H]〉=−0.01 and dispersion σ_([Fe/H])= 0.08. The near-solar metallicity and small dispersion of σ_([Fe/H]) of clump stars of the Galaxy obtained in this paper confirm the theoretical model of the Hipparcos clump by Girardi & Salaris. This suggests that nearby clump stars are (in the mean) relatively young objects, reflecting mainly the near-solar metallicities developed in the local disc during the last few Gyr of its history. We find iron-group element to iron-abundance ratios in clump giants to be close to solar.

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