Abstract
A theoretical counterpart to the Barnes-Evans relation between stellar surface brightness and V-R color has been calculated from model atmospheres for parameters appropriate to RR Lyrae stars. Such a relation can be used to derive stellar angular diameters from V,R photometry and, when applied to variable stars and combined with a radial velocity curve, to derive radii, distances, and absolute magnitudes by the method of Barnes et al. (1977, MNRAS,178, 661). This was done for RR Lyr and X Ari using the photometry of Moffett and Barnes (1980, private communication) and radial velocities from the literature. The resulting absolute magnitudes are Mv = ± 0.59 + 0.25 for X Ari and Mv = 0.61 ± 0.35 for RR Lyr. The method is shown to be a very accurate way of determining radii, distances, and absolute magnitudes for RR Lyrae stars which compares very favorably to the variations of the Baade-Wesselink technique currently in use.
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Manduca, A., Bell, R.A. The absolute magnitudes of RR Lyrae stars. Space Sci Rev 27, 509 (1980). https://doi.org/10.1007/BF00168343
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DOI: https://doi.org/10.1007/BF00168343