A study of ultraviolet spectroscopic and light variations in the X-ray binaries LMC X-4 and SMC X-1.
Zuiderwijk, E. J.; Hammerschlag-Hensberge, G.; van der Klis, M.; Willis, A. J.; Bonnet-Bidaud, J. M.; Glencross, W. M.; Mouchet, M.; Ilovaisky, S. A.; van Paradijs, J. A.; Chevalier, C.
Netherlands, France, United Kingdom, Germany
Abstract
Low-resolution IUE spectra of the massive X-ray binaries LMC X-4 and SMC X-1 have been obtained between 1200 and 3200 A at several epochs in August 1979 and April 1980. Comparison of these observations with theoretical light curves for an X-ray heated tidally distorted star indicates the existence of a disk around the compact star. The resonance-line doublets of N V, C IV and Si IV show marked changes with orbital phase, being particularly weak when the X-ray source is in front of the primary. These changes can be understood in terms of an anisotropic ionization structure in the expanding atmosphere of the primary caused by the presence of the X-ray source companion.