Period studies of five neglected Algol-type binaries: RW Cet, BO Gem, DG Lac, SW Oph and WY Per

We investigated the orbital period variations of five neglected Algol-type eclipsing binaries (RW Cet, BO Gem, DG Lac, SW Oph and WY Per) in this study. Their O–C   diagrams display tilted sinusoidal variations superimposed on upward parabolic forms. The parabolic variations, which correspond to secular period increases, were interpreted in terms of the combined effect of mass transfer and loss. Then, the mass transfer rates from the less massive secondary components to more massive primaries for non-conservative cases were calculated to be ∼10-7M⊙/yr for RW Cet, DG Lac and SW Oph and ∼10-8M⊙/yr∼10-8M⊙/yr for BO Gem and WY Per. The tilted (eccentric) sinusoidal representations of the O–C variations were interpreted in terms of the light-time effect due to unseen components in the systems. The possible third bodies in four Algol binaries (excluding RW Cet) would have masses larger than one solar mass. If these hypothetical large massive third bodies were normal stars, they should be detectable. Therefore, new astrometric, photometric and spectroscopic observations of these systems and careful analyses of the resulting data are required.