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Accurate Spectroscopic Surface Gravities for 8 Sub-Giants

Published online by Cambridge University Press:  19 July 2016

Bengt Edvardsson*
Affiliation:
Astronomiska Observatoriet, Box 515, S-751 20 Uppsala, Sweden

Abstract

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Logarithmic surface gravities between 2.9 and 3.8 (cgs) have been determined for eight G8IV-K2III stars from the analysis of pressure broadened wings of strong metal lines. Comparisons with trigonometrically determined surface gravities give support to the spectroscopic results. A thorough and rather conservative error analysis suggests that the errors are smaller than about 30% and confirms that the method is very insensitive to uncertainties in the fundamental stellar atmospheric parameters. Surface gravities of α Cen A and B and of Arcturus have also been obtained. Chemical abundances have been derived for 12 elements from Na to Ni, and for five heavier elements from Y to Nd have tentative abundances been derived from a single line of each element. Effective temperatures in the photometric system of Frisk (1983) are found to be consistent with spectroscopic temperatures from the excitation equilibrium of Fe I. Surface gravities determined from the ionization equilibria of Fe and Si are found to be systematically lower than the strong line gravities, which may be an effect of errors in the model atmospheres, or departures from LTE in the ionization equilibria.

Type
VI. Chemical Composition of Stars
Copyright
Copyright © Kluwer 1988 

References

Edvardsson, B.: 1987, Astron. Astrophys. in press.Google Scholar