THE DISTANCE TO THE LARGE MAGELLANIC CLOUD CLUSTER NGC 1866 FROM ITS CEPHEID MEMBERS

We have derived distances to four Cepheid variables of similar periods (2.6-3.5 days) in the field of the young LMC cluster NGC 1866 using t he visual surface brightness modification of the Baade-Wesselink metho d. For three of these variables, consistent distances are obtained whi ch support their cluster membership and yield a true cluster distance modulus of 18.47 +/- 0.20 mag. The distances have been corrected for t he nonsolar metallicity of -0.6 dex recently determined for NGC 1866 b y Hilker et al. A fourth Cepheid, HV 12204, is shown to have a bright blue companion star which invalidates the Baade-Wesselink analysis; th is Cepheid is likely to be a cluster member in a spectroscopic binary system. We determine the radii of the variables and find consistent va lues in the narrow range between 26 and 31 R., which agree very well w ith the values expected from the galactic Cepheid period-radius relati on.