Radii and Distances of Cepheids. I. Method and Measurement Errors

We develop a formulation of the Baade-Wesselink method which uses the Fouriercoefficients of the observables. We derive an explicit, analytic expression todetermine the mean radius from each Fourier order. The simplicity of thismethod allows us to derive the uncertainty in the mean radius due tomeasurement errors. Using simulations and a recent dataset we demonstrate that the precision ofthe radius measurement with optical magnitudes is in most cases limited by theaccuracy of the measurement of the phase difference between the light and thecolor index curve. In this case it is advantageous to determine the inverseradius, because it has normal errors.Comment: 18 pages, postscript, accepted for publication in Ap