MAGELLANIC-CLOUD CEPHEIDS - ABUNDANCES

We have determined parameters and abundances for three SMC and nine LM C Cepheids that have not been previously studied spectroscopically for metallicity, as well as three SMC and one LMC Cepheids observed previ ously by Luck & Lambert. This work nearly doubles the number of Cephei ds with spectroscopic metallicities in the SMC and triples the number in the LMC. For Galactic reference stars we have determined the abunda nces of 11 supergiants of spectral type F0 to K1. These abundances are used herein to examine the dispersion in cosmic [Fe/H] values found i n LMC Cepheids by Luck & Lambert, and in later papers will be used to correct the distance moduli obtained by us for these Cepheids using th e visual surface brightness technique. The Magellanic Cloud Cepheids t end to be longer-period Cepheids (the period range examined was from 3 7 to 133 days), and thus have physical gravities (derived from the per iod-luminosity relation and an inferred mass) that are 1.0 dex and low er. Spectroscopic gravities (derived by forcing the total Fe content, as determined from Fe I and Fe II, to be equal) are even lower. Fortun ately, the [Fe/H] content as determined from Fe I is not strongly depe ndent on gravity and is thus well determined. We combine our abundance s with other published high-resolution spectroscopic results, deriving a mean [Fe/H] for the SMC of -0.68 (sigma = 0.13, n = 25). The total range seen in the [Fe/H] ratios derived herein is -0.84 to -0.65. This result is in agreement with previous studies showing a small intrinsi c range in the metallicities in the SMC. For the LMC, from the Cepheid s studied here we obtain -0.30 (sigma = 0.12, n = 10), with a range of -0.55 to -0.19. Combining all available data, we obtain a mean [Fe/H] of -0.34 (sigma = 0.15, n = 32). From this analysis, there is little evidence for a significant metallicity dispersion in the LMC.