The surface magnetic field distributions of 53 Camelopardalis and Alpha-2 Canum Venaticorum

Abstract

Effective magnetic field curves for the magnetic Ap stars 53 Cam and Alpha-2 CVn have been obtained using a photoelectric Balmer-line magnetograph. These observations do not show the strong anharmonic behavior found in the magnetic curves of these stars as determined by photographic field measurement. The photoelectric magnetic curves are fitted very satisfactorily by oblique rotator models with modestly decentered magnetic dipole geometries. The data suggest that the anharmonic effective field curves obtained photographically for these stars arise mainly because of the difficulty of visually measuring the separation of the centroids of the right and left circularly analyzed line profiles, as suggested by Borra, although nonuniform distribution of the metals may also contribute significant effects in Alpha-2 CVn.