Supernovae of type I as end products of the evolution of binaries with components of moderate initial mass (M< or approx. =9 M/sub sun/)

Analysis of the theory of evolution of low- and intermediate-mass binaries allows us to select promising scenarios that lead to presupernova systems consisting of an accreting electron-degenerate dwarf (made primarily either of oxygen, neon, and magnesium, of carbon and oxygen, or of helium) and a low-mass (Mroughly-equalM/sub sun/) star supplying hydrogen-rich matter at rates in the range approx.10/sup -9/-10/sup -6/ M/sub sun/ yr/sup -1/ or a heavy disk composed of helium or of C and O supplying matter at an as yet undetermined rate. Some of these scenarios have an estimated frequency of realization comparable with the observed frequency (approx.10/sup -2/ yr/sup -1/) of Type I supernovae (SNeI), but it is as yet impossible to identify conclusively a single one as the most likely explanation of the SNI pheomenon and to reject all other possibilities. It is therefore not excluded that SNeI are a mixture of products of different scenarios. Estimates of formation frequency are very preliminary, since some of them are strongly dependent on the distribution of unevolved binaries over the initial mass ratio q/sub 0/, especially for q/sub 0/roughly-equal0.1--0.3, and most of them require knowledge of the processes that occur during a common envelope stage, the understanding ofmore » which is still very rudimentary.« less