Abstract. 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.

Abstract. We present 14.3 years of previously unpublished photometric observations of UX Ari. The observations were obtained between 1987.9 and 2002.2 using the T3 0.4-metre Automatic Photoelectric Telescope at Fairborn Observatory and consist of 1228 B band and 1213 V band measurements. The comparison star was 62 Ari. We have analyzed the new data together with previously published photometric observations. The V magnitude shows variations with dominant periods of about 12 and 25 years, where the longest period seems to correspond to an activity cycle. The previously reported anticorrelation between the B − V colour and V magnitude variations is confirmed.

Abstract. This paper presents a technique for separation of individual components in composite stellar spectra. The technique is based on a comparison of residual depths of the component spectral lines to residual depths of the corresponding spectral lines of a single star of the same spectral class. We apply the technique to high resolution spectra of the RS CVn system UX Ari, where the spectral lines from all three components are well resolved. The deduced variations in the relative flux of the primary component agree well with simultaneously obtained photometric observations of UX Ari. The starspots causing the light curve variations and the facular areas causing the chromospheric emission seem to be separated by about 180• in longitude on the surface of the primary component. We also find that the secondary component of UX Ari is subject to some chromospheric activity. Finally, some fundamental parameters of the third star in the spectrum are derived and discussed.