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The model of Cyg X-3 as a young radiopulsar in the binary system was first proposed by Basko et al. (1974). Both sources are characterized by variable non-thermal radio waves (Nicolson, 1984; Molnar et al., 1984). A strict periodicity is also observed for the system LSI+61 303: the radiation is in the form of radiobursts with the orbital period of the underlying binary system.
Of great interest is the latest report concerning the optical identification of CygX-3 with the WR star (van Kerkwijk et al., 1992). According to this identification, CygX-3 is a binary system with a period of 4.8h; the mass of the normal component is , radius , and semi-major axis (Conti, 1992). The question arises as to how a fast rotating NS could be preserved at the late stage of evolution of the binary system? This may be due to the fact that CygX-3 has a low magnetic field compared with other neutron stars in massive binary systems. The spindown time for ejector losing energy by magnetodipole radiation may be estimated as
There is no time for the passage E P if the NS period satisfies the condition (4.8.3), i.e.
Assuming the mass loss rate of a WR star of yr , and the velocity of the stellar wind km s , we obtain the spin-down time until
It follows from the above estimates that a magnetic field , or is necessary. Returning to condition (38) we find that the period of CygX-3 must be