Ultraviolet variability of the mCP star 56 Arietis

TL;DR

This paper investigates the far-UV spectrophotometric variability of the mCP star 56 Arietis using archival IUE data, revealing wavelength-dependent brightness changes linked to silicon surface distribution.

Contribution

It provides the first detailed analysis of 56 Ari's UV variability across different phases, highlighting the influence of silicon distribution on its spectral features.

Findings

Brightness varies with phase and wavelength.

Light curve shapes change continuously with wavelength.

Silicon surface distribution significantly affects UV variability.

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.