2003A&A...399L..11A

We present simplified calculations of UX Ari B-V colour index and V magnitude for a range of parameter values. The results of our calculations are compared to previously published measurements. We find that our calculations reproduce the well established colour-brightness relation (UX Ari gets bluer as it gets darker) only if the dark spots on the surface of the K star are accompanied by bright facular areas. There is currently an ambiguity between the temperature of the facular areas and the portion of the stellar surface occupied by them.