The Behavior of Bp He-weak Stars in the Far UV—Paper IV: HD 28843

Abstract

The analysis of five spectra of the Bp He-weak Si star HD 28843 recorded by the SWP camera on board the International Ultraviolet Explorer reveals variations of the far-ultraviolet spectral energy distribution over a time interval of 4 yr and eight months. Variations are present shortwards of 1700 Å which can be partly attributed to variations of lines and continuum of Si ii. Other lines due to C ii and Si iii also contribute to the opacity in this range too. The variations suggest that silicon is not distributed in a uniform manner over the surface and that the horizontal gradients of the silicon abundance are probably quite large.