The ultraviolet light curves of W Ursae Majoris

Abstract

Controversy has surrounded explanations of W-type W Ursae Majoris light curves. Current alternatives in the literature are a starspot model and a hot secondary model. Far UV data from the Astronomical Netherlands Satellite (ANS) produced light curves that seemed inconsistent with a hot secondary. The inconsistent results could follow if there exists a UV excess on the primary, more massive component. Recently published data for faculae associated with sunspots exhibit a large far UV excess. These data suggest that corresponding faculae on W Ursae Majoris could explain the ANS data within the context of the hot secondary model