Long-Baseline Interferometric Observations of Cepheids

摘要

We present observations of the Galactic Cepheids η Aql and ζ Gem. Our observations are able to resolve the diameter changes associated with pulsation. This allows us to determine the distance to the Cepheids independent of photometric observations. We determine a distance to η Aql of 320 ± 32 pc and a distance to ζ Gem of 362 ± 38 pc. These observations allow us to calibrate surface brightness relations for use in extragalactic distance determination. They also provide a measurement of the mean diameter of these Cepheids, which is useful in constructing structural models of this class of star.