Lick spectral indices for super-metal-rich stars

Citation
A. Buzzoni et al., Lick spectral indices for super-metal-rich stars, PUB AST S P, 113(789), 2001, pp. 1365-1377
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
ISSN journal
0004-6280 → ACNP
Volume
113
Issue
789
Year of publication
2001
Pages
1365 - 1377
Database
ISI
SICI code
0004-6280(200111)113:789<1365:LSIFSS>2.0.ZU;2-P
Abstract
We present Lick spectral indices for a complete sample of 139 candidate sup er-metal-rich stars of different luminosity classes (MK type from I to V). For 91 of these stars we were able to identify, in an accompanying paper, t he fundamental atmosphere parameters. This confirms that at least 2/3 of th e sample consists of stars with [Fe/H] in excess of +0.1 dex. Optical indic es for both observations and fiducial synthetic spectra have been calibrate d to the Lick system according to Worthey et al. and include the Fe I indic es of Fe5015, Fe5270, and Fe5335 and the Mg I and MgH indices of Mg-2 and M g b at 5180 Angstrom. The internal accuracy of the observations is found to be sigma (Fe5015) = +/-0.32 Angstrom, sigma (Fe5270) = +/-0.19 Angstrom, s igma (Fe5335) = +/-0.22 Angstrom, sigma (Mg-2) = +/-0.004 mag, and sigma (M g b) = +/-0.19 Angstrom. This is about a factor of 2 better than the corres ponding theoretical indices from the synthetic spectra, the latter being a consequence of the intrinsic limitations in the input physics, as discussed by Chavez et al. By comparing models and observations, we find no evidence for nonstandard M g versus Fe relative abundance, so [Mg/Fe] = 0, on the average, for our sam ple. Both the Worthey et al. and Buzzoni et al. fitting functions are found to suitably match the data and can therefore confidently be extended for p opulation synthesis application also to supersolar metallicity regimes. A s omewhat different behavior of the two fitting sets appears, however, beyond the temperature constraints of our stellar sample. Its impact on the theor etical output is discussed, as far as the integrated Mg-2 index is derived from synthesis models of stellar aggregates. A two-index plot, such as Mg-2 versus Fe5270, is found to provide a simple and powerful tool for probing distinctive properties of single stars and stellar aggregates as a whole. T he major advantage, over a classical CM diagram, is that it is both reddeni ng free and distance independent.