Spectrophotometric Variability of the Magnetic CP Star alpha2 CVn

TL;DR

This study analyzes ultraviolet spectrophotometric variability of the magnetic CP star alpha2 CVn using archival IUE data, revealing wavelength-dependent light curve behaviors and a null wavelength region.

Contribution

It provides detailed characterization of the star's ultraviolet variability and identifies a null wavelength region, enhancing understanding of magnetic chemically peculiar stars.

Findings

Brightness remains constant between 3015-3138 A during rotation.

Minimum light curve amplitude occurs at 1660 and 1900 A.

Monochromatic light curves change shape and phase displacement with wavelength.

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.