Study of the period changes of X Trianguli

In the present study the (O-C) diagram of the eclipsing binary X Tri is use d to study its orbital period behaviour. From our analysis, which is based on the description of the (O-C) diagram using weighted, high-order polynomi als, it is shown that the period changes of X Tri (at least those after 194 9) can be explained as due either to magnetic activity cycles or to a third companion on the subgiant G3IV cool secondary component. The elements of t his hypothetical third body were computed and from their values it was foun d that it cannot coincide with the already known, visual companion. Moreove r, if the period variations of X Tri are coming from the magnetic activity of the subgiant component of the binary, the subsurface magnetic held was f ound to be equal to 8.77 kG.