The orbital period study and photometric analysis of XY

Abstract. Photoelectric observations of the eclipsing bi-nary XY UMa have been carried out in B and V colours at the Ege University Observatory. Combining these newly obtained data with the previous ones available in the lit-erature, the problem pertaining to the orbital period of the system has been investigated through a detailed de-scription of the O−C diagram. The sinusoidal and secular changes have been found. Such variations of the orbital period have been examined in terms of three plausible mechanisms, namely (i) a light-time eect due to a third body, (ii) the orbital period modulation due to magnetic activity cycle of a component star, and (iii) a mass loss case in which the ejected material escapes out from the binary system. A combination of a magnetic activity cy-cle mechanism and a mass loss case is found to reproduce satisfactorily the period changes. Further, the observed photoelectric light curves of the system have been ana-lyzed with the Wilson-Devinney approach. This analysis shows that the asymmetries of the light curves of XY UMa can be interpreted in terms of cool star-spot covering 7% of the stellar photosphere of the primary component of this binary. The system is found to be a Lyrae type detached binary. The absolute elements of the system are also deduced