Spectrophotometric variability of the magnetic CP star 56 Arietis in spectral region from 1950 to 3200 A

TL;DR

This study analyzes the ultraviolet spectrophotometric variability of the magnetic chemically peculiar star 56 Arietis using archival IUE data, revealing wavelength-dependent brightness changes linked to surface element distributions.

Contribution

It provides new insights into the flux redistribution mechanisms caused by uneven silicon and iron surface distributions in 56 Arietis.

Findings

Brightness varies over the rotational period in UV wavelengths.

No true null wavelength region observed.

Flux redistribution linked to silicon and iron surface inhomogeneities.

Abstract

The spectrophotometric variability of the magnetic CP star 56 Arietis (56 Ari) in the ultraviolet spectral region from 1950 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 56 Ari is not constant in the investigated wavelengths over the whole rotational period. The monochromatic light curves continuously change their shape with wavelength. This indicates that we do not observe a truly 'null wavelength region' where the monochromatic light curve has a zero amplitude. Probably, an uneven surface distribution of silicon and iron mainly influences the flux redistribution from the far-UV to near-UV spectral regions, although additional sources of opacity may be involved. The redistribution of the flux at phase 0.25 is connected with the nonuniform distribution of silicon on the stellar surface of 56 Ari. On the other hand, the redistribution of the flux at phase 0.65 is quite complex, because there are additional blocking and redistribution of the flux by iron lines in the near-UV spectral region.