Long-term observations of CYG X-3 with VELA 5B

Long term (1969 to 1979) observations of Cygnus X-3, obtained by the Vela 5B satellite are presented. The 3 to 12 keV light curve has 10 day time resolution. Cyg X-3 is a peculiar high luminosity X-ray source, radiating from the radio region to hard gamma rays of more than 10(16) eV. It has a 4.8 hour period, probably orbital, which is not resolved by the present analysis. Long term periodicities of approx. 17, 20, and 33 to 34 days have been reported by several authors, and explained as the effects of apsidal motion, precession, or an eccentric orbit. There is weak evidence for a 20 day flux variation. The light curve shows high and low states which alternate with a characteristic timescale of approximately 1 year. There is no counterpart, at this time resolution, of the giant radio outburst of September 1972.