Ultraviolet variability of the mCP star 56 Arietis

Abstract

The spectrophotometric variability of the mCP star 56 Ari in the far-UV spectral region from 1150 \AA\ to 1980 \AA\ is investigated. This study is based on the archival {\it IUE} data obtained at different phases of the rotational cycle. The brightness of 56 Ari is not constant in the investigated wavelengths over the whole rotational period. The monochromatic light curves continuously change their shape with wavelength. The comparison of energy distributions at three phases show that the first minimum of light curves at phase 0.25 is replaced by the maximum for $\lambda>$1608\AA, but the second minimum of light curves at phase 0.65 absent in the spectral region between $\lambda$1938\AA\ and $\lambda$1980\AA. The variable broad features in the far-UV connected with a non-uniform distribution of silicon over the surface of 56 Ari influence substantially the light variations in the UV.