So far we have considered evolution of a magnetic rotator related to single rotators or those entering binary system with circular orbits. This approximation was appropriate for the gross analysis of binary evolutionary scenario performed by Kornilov and Lipunov (1983a,b)[85, 86]. This approximation is further justified by the fact that the tidal interaction in close binaries leads to orbital circularization in a short time (Hut, 1981[70]) However, the more general case of a binary with eccentric orbit must be considered for further analysis. It is especially important because many of the currently observed X-ray pulsars, as well as recently discovered radiopulsars with massive companions PSR B1259-63 (Johnston et al., 1992[78]) and PSR B0042-73 (Kaspi et al., 1994)[81], are in highly eccentric orbits around massive companions. Previously, such studies have been performed by Gnusareva and Lipunov (1985)[56], Prokhorov (1987a)[166] and Osminkin and Prokhorov (1995)[147].
Orbital eccentricity necessarily emerges after the first supernova
explosion and mass expulsion from the binary system. In massive
binaries with long orbital periods 
days, the eccentricity may
be well conserved until the second episode of mass exchange (Hut,
1981)[70]. Here, we concentrate on the evolutionary
consequences of eccentricity.