Spectrophotometric Variability of the Magnetic CP Star alpha2 CVn

Abstract: The spectrophotometric variability of the classical magnetic CP star alpha2 CVn in the ultraviolet spectral region from 1150 to 3200 A is investigated. This study is based on the archival International Ultraviolet Explorer data obtained at different phases of the rotational cycle. The brightness of the star at spectral region from 3015 to 3138 A is constant over the period of rotation which means that the so called 'null wavelength region' exist on these wavelengths. Moreover, the minima values of the amplitude of light curves are reached in the spectral region at \lambda \lambda 1660 and 1900 A. The monochromatic light curves in the 'pseudo-continuum' of this star change their shape with wavelength. All light curves with \lambda < 2505 A have a similar shape, but the monochromatic light curves with \lambda > 2505 A shows the phase displacement of the minimum from 0.0 at \lambda 2505 A to 0.3 at \lambda 2993 A.