The metallicity effect on the Cepheid P-L relation from SMC Cepheids

We present results based on a Baade-Wesselink analysis of Cepheids in the Small Magellanic Cloud. The Baade-Wesselink analysis provides individual luminosities for these metal-poor Cepheids which combined with recent Baade-Wesselink results from Gieren et al. (1998) on solar metallicity Galactic Cepheids constrain the metallicity effect on the zero-point of the Cepheid P-L relation. A preliminary analysis leads to an effect of #DELTA#M_V/#DELTA#[Fe/H] = -0.45 #+-# 0.15, metal-rich Cepheids being brighter, in good agreement with several recent independent determinations. An effect of this magnitude reduces significantly the current disagreement between the long and the short distance estimates to the LMC, and favors a shorter value. (orig.)8 refs.Available from TIB Hannover: RR 7310(98-34) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A Baade-Wesselink analysis of Cepheids in the Small Magellanic Cloud

We present preliminary results from a Baade-Wesselink analysis of five Cepheids in the Small Magellanic Cloud with periods between 13.5 and 16.8 days and spanning a range of (B-V) color from 0.5 to 0.8. Employing the surface brightness calibration of Fouque and Gieren (1997) we find a distance modulus to the SMC of 18.86#+-#0.08 mag (internal error) and that the SMC Cepheids are fainter than their galactic counterparts by approximately 0.2 mag. A full analysis of the various possible biases and systematic effects is required before firm conclusions can be reached on basis of the data presented here. This work is ongoing and the main point of this contibution is to illustrate the potential of the Baade-Wesselink method for resolving the luminosity-metallicity effect question. If the preliminary result holds up, it suggests that there is a metallicity dependence of the P-L relation of the order 0.3 mag per dex in the sense that metal rich Cepheids are brighter. (orig.)Available from TIB Hannover: RR 7310(98-13) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman