Modeling the Photometric Variability of Alpha² CVn with a Dynamical Magnetosphere

Abstract

Alpha² Canum Venaticorum (α ² CVn) is a strongly magnetic star with peculiar chemical signatures and periodic variability that have been long attributed to the diffusion of magnetic elements through the photosphere, leading to chemical spots across the stellar surface. However, recent studies of other magnetic hot stars are consistent with magnetospheric clouds above the surface. Here we take a renewed approach to modeling α ² CVn with a simplified dynamical magnetosphere and a tilted, offset magnetic dipole to reproduce its Transiting Exoplanet Survey Satellite variability. Our dipole model also reproduces well the magnetic surface map of α ² CVn from Silvester et al. Its ultraviolet variability, from IUE archival spectra, is also consistent with traditional reddening models. However, other observable quantities from the system contradict the expectations of a magnetosphere, and we conclude that it is unlikely to be present in α ² CVn.