"catacylsmic" refers to three classes of eruptive variables: dwarf
novae, novae and superrnovae, arranged in order of increasing integrated energy
of outbursts. U Geminorum type stars are dwarf novae with integrated energies
in the range of 10^38 to 10^39 ergs. (Kraft 1963). In general they have long
intervals of apparent quiescence at minimu with sudden rises to maximum. The
range of outbursts is between 2 to 6 magnitudes, depending upon the star. It is
a well established fact that most of themember of this group are spectroscopic
binaries with short periods, in the order of a few hours(Kraft, Luyten 1965).