Chromospherically active, spotted stars generally become redder as well as
fainter when large starspots rotate into view on the stellar disc. However, the
RS CVn system UX Ari (a triple-lined system), becomes bluer as it gets fainter.
One possible explanation is that hot, bright facular regions accompany the
cool, dark photospheric spots of the active component. The bluer flux of the
hotter, inactive component does not appear to be sufficient to explain the
observed behaviour. We have begun a search for additional chromospherically
active stars with a similar relation between colour and brightness, to
investigate whether these relations can be explained in the same way. Our
results for V711 Tau are presented here, and we conclude that the faculae
explanation holds also in this case.Comment: 3 pages, 1 figure, proceedings from the 13th Cambridge Workshop on
cool stars, stellar systems, and the Sun, Hamburg, Germany, July 2004,
ESA-SP, in pres