Observations of the Late Superhump in VW Hydri

Abstract

This paper presents the results of simultaneous optical and near-IR photometry, optical fast spectroscopy, and Exosat X-ray observations of the dwarf nova VW Hyi, obtained simultaneously during three consecutive orbital cycles, approximately two days after the 1983 November superoutburst terminated. The optical data show clear evidence for a 'late superhump', which is shifted + 0.7 in phase relative to the orbital modulation. An attempt is made to derive from the observed spectral distribution the contribution of the late superhump. The orbital hump and the late superhump apparently are not related to each other. This important effect excludes all models, in which the late superhump phenomenon is interpreted in terms of variations in the bright-spot brightness.