Metal Line-Blanketing and Opacity in the UV of α² CVn

Abstract

Ultraviolet photometric observations by OAO-A2 were made of α² CVn covering the entire 5^ḍ5 period of this magnetic Ap variable. The light curves ranging from 1250A to 3330 A indicate the dominant role of rare-earth line-blanketing in redistributing flux. In a broad depression of the continuum covering 2300 A to 2600 A scanner observations identify strong lines of Eu III as major contributors to this feature. At maximum intensity of the rare-earth lines the ultraviolet continuum shortward of 2900 A is greatly diminished while the longer wavelength regions into the visual become brighter. Thus, the light variations in α² CVn are: due to the variable strong line-blanketing by the abundant rare-earth elements.