Infrared and optical observations of cataclysmic variables.

This thesis presents infrared and optical photometry of the binary light curves of several cataclysmic variables. The results are discussed in terms of the accepted model of cataclysmic variables, comprising a Roche lobe filling late type secondary and a white dwarf primary. The secondary star loses matter from the inner Lagrangian point and this matter forms an accretion disc around the white dwarf. Our observations have shown that sometimes the late type secondary dominates the infrared luminosity of the binary. With further accurate observations over many cycles such systems will provide an excellent opportunity for the analysis of ellipsoidal variations in late type stars. In other systems the accretion disc spectrum, which current theories predict should vary as v 1/3, dominates the luminosity of the system from the ultraviolet right through to the near infrared. Then our observations, combined with ultraviolet and further optical measurements, allow us to discover the size and outer rim temperature of the accretion disc. Alternatively a combination of the disc spectrum, dominating at short wavelengths and the spectrum of the late type secondary, becoming bright at long wavelengths is observed. Observations of the light curves, simultaneously at infrared and optical wavelengths, then enable us to show that the results can be modelled in terms of an accretion disc of standard brightness distribution being eclipsed by a late type secondary. This provides support for current disc theories. Finally our observations out to 3.6 um combined with 2 - 2.5 um spectrophotometry of one system have shown clearly the presence of a dust cloud around the binary and allowed us to find the temperature of this dust. Similar observations of other systems will be of interest.