Multi-wavelength observations of X-ray binaries

In all areas of astronomy a multi-wavelength approach is crucial, the work presented here demonstrates this. The thesis is divided into two parts. Part I is a study of the physics of accretion from a young hot Be star, onto a neutron star. The general properties of high mass X-ray binaries are reviewed and two systems are investigated. A detailed pulse phase-resolved analysis of the X-ray spectrum observed by EXOSAT during the 1983-84 outburst from V0332+ 53 is given. We suggest that the low energy absorption is predominantly interstellar in origin. If our line of sight is not close to the neutron star magnetic axis then we would not expect to see any dependency on pulse phase of either the cutoff energy or the e-folding energy, as observed. The pulse phase dependency of the spectral index and normalisation may be due to emission from two hotspots. This could explain the change in the profile shape from a single to a double pulse. The discovery of occasional excess power at low frequencies is probably caused by inhomogeneities in the accretion stream during the onset of an X-ray flare. The correlation between the infrared excess, Hα emission and X-ray outbursts over the past decade is also investigated. We suggest the circumstellar disk is at a low inclination angle and that the larger X-ray outbursts in 1989 was the result of enhanced mass loss from the circumstellar disk. Part II presents the results from an investigation designed to investigate the nature of a sample of highly variable radio sources (HVRSs) positioned in the galactic plane.