AN ABUNDANCE ANALYSIS OF ALPHA-CENTAURI-A

A differential abundance analysis between the Sun and α Cen A has been carried out. Over 500 lines of 26 elements have been measured in very high signal-to-noise ratio spectra of both objects. The result is a linearly averaged metal overabundance in α Cen A of around 0.12 dex, with an error in the mean value for most elements of ± 0.02 to ± 0.04 dex. The derived overabundances have been incorporated into the model atmosphere calculations. Light elements up through Zn are distinctly overabundant, whereas heavy elements show solar abundances. A relatively small overabundance of Fe and strong overabundances of the odd-Z elements Na Al Mn and Cu point toward enrichment of the prestellar medium by a Type II supernova. The derived abundances give a consistent age of around 4 billion yr for the A and B components of the α Cen system according to interior model calculations published by Demarque, Guenther, and van Altena in 1987.