Abundances of Heavy Elements in the Magellanic Clouds. I. Metal Abundances of F-Type Supergiants

We present an analysis of high-resolution spectroscopy for eight F-type supergiants in each of the Magellanic Clouds together with new Stromgren uvby and Cousins BVRI photometry for these stars. Most of the stars are less luminous than any studied previously in the literature, thus ensuring more reliable measures of their physical parameters. The following conclusions were reached: 1. The mean iron abundance for the SMC is [Fe/H] = -0.65+/-0.2 dex. 2. The mean iron abundance for the LMC is [Fe/H] = -0.30+/-0.2 dex. 3. The abundances of the stars in both clouds appear relatively uniform, although there is a suggestion of a scatter in abundances of perhaps ~ 0.2 dex in addition to the observational uncertainties. 4. OveralI, the abundances of the elements studied in this paper, relative to iron, are very similar in the Magellanic Clouds and in Canopus. 5. The carbon-to-iron abundance, in particular, is the same in both clouds as in Canopus. This is highly significant since previous results, from UV spectra of H II regions, have indicated that carbon is highly underabundant in both clouds. 6. Vanadium is somewhat overabundant in the LMC. 7. Heavy neutron-capture elements, Nd and Sm, are overabundant in both clouds, thus supporting the trends found by Spite, Spite, and Francois for three stars in the SMC.