Binary systems in the infrared
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Near infrared (JHKL) photometry of RS CVn -type binary systems has been carried out to search for any evidence of circumstellar material in these systems and also for the existence of light variations outside eclipse similar to those observed in the visual. No apparent infrared excess has been observed in fourteen randomly selected systems.Infrared light curves of seven RS CVn binaries (HR 1099, UV Psc, SZ Psc, TY Pyx, AD Cap, HD 5303 and ER Vul) have been obtained, and nearly sinusoidal light variations outside eclipse have been detected for at least HR 1099, SZ Psc and TY Pyx. Irregular light variations have also been observed in the infrared as in the visual, and also a variation of the maximum brightness of HR 1099 and UV Psc. An esti- mate of the spectral types of the components of the seven extensively observed systems has been made using the current photometric data.Taking into account the current and other observations, possible models have been discussed, with a preference for the spot model. The active component has been shown to be a fast rotator.Another part of this dissertation is near infrared photometry of Wolf -Rayet stars. The most interesting result of these observations was the discovery of an increase in brightness of HD 193793 (WC7 +05) by 2m4 in L' (Xo = 3.8 pm) between June 1976 and August 1977. This has been attributed to the condensation of grains in the star's circumstellar shell.