Metallicities and the Cepheid Distance Scale
Session 7 -- Stellar Abundances Across the H-R Diagram
Display presentation, Monday, 30, 1994, 9:20-6:30

## [7.06] Metallicities and the Cepheid Distance Scale

A.M. Fry, B.W. Carney (Univ. North Carolina)

We are examining the metallicities of the Cepheids used to calibrate the extragalactic distance scale in order to better compare the Cepheid distance scale to other distance scales, such as the RR Lyraes. In calibrating the Cepheid scale, distances to clusters containing Cepheids are found by main sequence fitting to the Pleiades. In the past, all the clusters have been assumed to have the same metallicity as the Pleiades, even though a 0.1 dex difference in metallicity can change the derived distance by 10\%. However, Edvardsson et al. (1993) have found a 0.5 dex spread in metallicities at all ages for field stars and Friel and Janes (1993) have found the same result for young and old open clusters. Thus, the Cepheids may show a range in abundances, too. Indeed, Luck and Lambert (1985) found a spread in metallicities of 0.5 dex in galactic Cepheids and in non-variable F and G supergiants and Luck (1994) found a smaller spread spread among clusters containing some of the Cepheids that calibrate the Period-Luminosity relation. Using an inhomogenous data set, Giridhar (1986) also has found a 0.6 dex spread in Cepheid metallicities.

We present here metallicities for several of the calibrating Cepheids, including CF Cas (in NGC 7790), $\eta$ Aql (a field Cepheid), and SV Vul (in the OB association Vul OB1).