A photometric study of the W UMa-type system U Pegasi

In the present study, the activity of the eclipsing binary of tile W UMa-ty pe system U Peg is examined by analysing the photoelectric observations cov ering the period from 1950 to 1989. During this period, the light curves sh ow significant differences and asymmetries. The analysis of the correspondi ng light curves is made using Djurasevic's inverse problem method. To expla in the light-curve asymmetries and variations, we used a Roche model that i nvolved regions containing spots on the components. The analysis shows th;t t thc system U Peg is in an overcontact configuration (f(over) similar to 1 4.9%). The Roche model with spotted areas on the cooler component yields a good fit of the observations for the whole set of the analysed light curves without any changes of the basic system parameters. This indicates: that t he complex nature of tile light-curve variations during the examined period can be explained by the evolution and motion of spotted areas on the coole r component. According to the obtained results, the spotted areas: cover a significant part of the stellar surface; the changes in their location and size with time are examined.