Analysis of the light curve of the magnetic CP star HD 56022.

An examination of the published observational data concerning the light curves of magnetic CP stars has shown that only one star - HD 56022 - shows a light curve with a very long phase interval of light constancy. Only for this type of variability it is imaginable that the equatorial symmetry of the surface brightness distribution could be excluded. However, the analysis of the light curve of HD 56022 in the colour u of the Strömgren system has indicated that the possibly equatorial position of the small bright spot is not in contradiction to this observed curve. From the analysis in u the maximum amplitude of a light curve at another wavelength, where the curve is in counterphase to the light curve in u, can be predicted. The amplitude of such a light curve must be much smaller than 0.1 mag. From unpublished observations of HD 56022 by the satellites TD-1 A and ANS the authors have determined the amplitude at λ = 155 nm, where the light curve is in counterphase to that in u, to be 0.2 mag. The consequences from the contradiction between the model and the observations in UV are discussed.