the determination of energy budgets of the primary X-ray and secondary reprocessed UV, optical and IR emissions reside on multi-wavelength observations. The main modulations in FOAqr have been studied in the X-rays and at optical/IR wavelengths. The optical spin pulsations, occurring mostly in phase with the X-ray ones, were found to arise from the outer regions of the accretion curtain (Paper1; Welsh & Martell 1996). The orbital modulation from UV to IR was instead found to be multicomponent and attributed to the X-ray heated azimuthal structure of the accretion disc (henceforth bulge) and to the inner illuminated face of the secondary star (Paper1). However the temperature of the UV emitting bulge could not be constrained due to the lack of a precise quantification of the spectral shape of the UV spin modulation. In this work we present high temporal resolution spectroscopy acquired with HST/FOS which provides the first detection of different UV periodicities in FOAqr. For a comprehensive study, these data are complemented with low temporal resolution IUE spectra along the orbital period. Coordinated optical photometry extends the study to a wider spectral range, providing the link to investigate the long term behaviour of these variabilities.

Observations and data reduction
