Photometry and discussion of the classical Algol systems U Sge and U Cep

The (in many respects, similar) classical Algol-type eclipsing binary systems U Sge and U Cep are studied and compared against a background of photometric evidence, both broadhand and narrowband. Broadband photometry of the primary minimum of U Sge over a four year period fails clearly to confirm Olson's (1982b) finding of radial variations.On the other hand, the W-type pattern of variation indicated in Olson's (1976) H photometry of the primary eclipse of U Cep is also noticed for U Sge. These effects are analysed in terms of an emitting accretion disk, surrounding the primary components. Electron densities in these highly ionized structures are derived to be in the range 10¹⁰–10¹¹, for the H emitting region, with that of U Cep being 3 times greater than that of U Sge, though since the volume of the structure is 3 times bigger for U Sge, the overall masses are comparable.These findings can be placed in a Case B-type interacting binary context, which shows the studied accretion structures to be relatively tenuous; and, since the mean mass loss rate for U Cep is likely to be high than that of U Sge by more than an order of magnitude, suggests they are not so directly dependent on this mass-loss rate.