Springer Online Journal Archives 1860-2000
Abstract 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) Hβ 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 Hβ 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.
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