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

• Published in: Monthly notices of the Royal Astronomical Society 2010-10, Vol.408 (2), p.1225-1232
• Main Authors: Puzeras, E., Tautvaišienė, G., Cohen, J. G., Gray, D. F., Adelman, S. J., Ilyin, I., Chorniy, Y.
• Format: Article
• Language: English
• Subjects: Astronomy; Atmospherics; Chemical elements; Chromium; Clumps; Disks; Dispersions; Earth, ocean, space; Exact sciences and technology; Galaxies; Iron; Metallicity; Metals; Spectrum analysis; Stars; Stars & galaxies; stars: abundances; stars: atmospheres; stars: horizontal branch
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2010.17195.x

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 Teff= 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.