The Baade-Wesselink method and the distances to RR Lyrae stars. II - The field star X ARIETIS

VR and JHK photometry and radial velocities with typical accuracies of 1 km/sec for the metal-poor RR Lyrae field star X Arietis. These data, along with unpublished UVBY photometry, have been used to derive the distance to X Ari using two variations of the Baade-Wesselink method. The possibility of photospheric velocity gradients that might distort the value of the systemic velocity and cause a phase shift was examined, and it was found that no gradient exists in the part of the stellar atmosphere considered. The phasing problem previously noted for VY Ser by Carney and Latham (1984) also occurs for X Ari when optical photometry is used to compute the effective temperatures, but not when the V - K color index is used. Possible causes of these phase shifts are discussed, and it is concluded that X Ari has an aggregate average V magnitude of 0.73-1.03 mag on the basis of the V - K results.