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Cyg X-3

The model of Cyg X-3  as a young radiopulsar in the binary system was first proposed by Basko et al. (1974)[10]. Both sources are characterized by variable non-thermal radio waves (Nicolson, 1984[146]; Molnar et al., 1984[143]). 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[207]). According to this identification, CygX-3 is a binary system with a period of 4.8h; the mass of the normal component is tex2html_wrap_inline11369 , radius tex2html_wrap_inline11371 , and semi-major axis tex2html_wrap_inline11373 (Conti, 1992[36]). 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 tex2html_wrap_inline11375 P if the NS period satisfies the condition (4.8.3), i.e.


Assuming the mass loss  rate of a WR star of tex2html_wrap_inline9278 yrtex2html_wrap_inline8853 , and the velocity of the stellar wind tex2html_wrap_inline11381 km stex2html_wrap_inline8853 , we obtain the spin-down  time until tex2html_wrap_inline9737


It follows from the above estimates that a magnetic field tex2html_wrap_inline11387 , or tex2html_wrap_inline11389 is necessary. Returning to condition (38) we find that the period of CygX-3 must be


Mike E. Prokhorov
Sat Feb 22 18:38:13 MSK 1997