Contribution to the study of supermetallicity in late-type giants

This research is a detailed analysis of Aur and Leo, two of the best examples of "super- metal-rich" (SMR) stars found by Spinrad and Taylor by a scanner technique. They have been analyzed on high-dispersion spectrograms taken at the 100-inch Mount Wilson coude' telescope (6.8 A mm-1) for Aur and at the coude' focus of the 60-inch ESO telescope in Chile (12 A mm-1) for Leo. The star E Vir has been used as a comparison star. Particular care has been taken only to compare spectrograms taken with the same instrumentation. The spectra have been interpreted with theoretical line computations using a grid of model atmospheres. The models have been calculated on the assumption of LTE, hydrostatic equilibrium, and radiative equilibrium. Convective transport in the convective zone has been taken into account. Line blanketing has been included using a statistical model of line absorption. The detailed analysis of Aur versus e Vir has not revealed any peculiarity other than a marginal deficiency of Aur in barium. With respect to the Sun, Aur has a mild overabundance of Na, as does E Vir; and a possible overabundance in Mg, Si, and Ca is just at the limit of significance. The analysis of Leo versus either E Vir or the Sun shows an overabundance in Na, Ca, Mn, and Cu and a deficiency in Ba. Iron and most other metals do not show any significant overabundance, even allowing for a rather larger uncertainty in the effective temperatures. The conclusion reached about "supermetallicity" is that the word "super-metal-rich" should be avoided, being misleading for stars which have a normal solar iron/hydrogen ratio. Supermetallicity appears to be highly selective, and limited to just a few elements. Subject headings:abundances, stellar - atmospheres, stellar - late-type stars - line profiles - stars, individual