K. O. Mason
Cyg X-3 and the binary X-ray sources
1976 (supervisor: P. W. Sanford)

The X-ray instruments onboard the Copernicus satellite have been used to observe the X-ray light curves of four binary sources; 3U 0900-40, 3U 1700-37, Cyg X-1 and Cyg X-3. Variations in the intensity and spectrum of the sources are examined and the data used to investigate the gas flow between the primary star in each system, and the compact, X-ray emitting secondary. In the case of 3U 0900-40 and 3U 1700-37, evidence is found for a relatively high density tail of absorbing material extending behind the X-ray source in its orbit, and the X-ray data are compared with the published results of optical observations of the respective primary star. For all four systems it is concluded that the data require the gas flow to be variable in degree or direction.

Cyg X-3 is examined in detail. Its X-ray output exhibits a smooth periodic modulation and, as such, its behaviour is unique among known X-ray binaries. We derive an accurate period for the modulation and find no evidence that this period is changing with time. In addition, we compute a representative mean shape for the pulse profile and examine changes in the latter. Cyg X-3 is also seen as an infra-red source, and is a powerful and variable radio source. The relationship between the output in each frequency range is explored, using X-ray, infra-red and radio data taken simultaneously, and the results compared with those predicted from various source models. A general correlation is found between the X-ray and radio intensity levels.

Finally, galactic X-ray sources are discussed in a wider perspective. We examine Copernicus data on several sources not so far identified with optical systems and compare these to known binary sources. The characteristics of these two groups are contrasted. Techniques for identifying X-ray sources with optical or other objects are also discussed.