Orbital Period Changes of the Eclipsing Binaries RW Cap, BG Peg, and CU Peg

The changes in the orbital periods of the Algol-type eclipsing binaries RW Cap, BG Peg, and CU Peg have been studied. The changes in the orbital period of RW Cap and BG Peg can be well represented by cyclic variations with large amplitude. It has been shown, that these changes cannot be explained by the presence of a third body. They can be a consequence of the magnetic activity of the secondary components having a convective zone. The changes in the orbital period of CU Peg can be represented by a superposition of a secular period increase due to exchange of matter between the components and cyclic variations. These cyclic variations can occur due to the presence of a third body in the system or they can be a consequence of the magnetic activity of the secondary component.