Dr. Christopher Mauche (Lawrence Livermore National Laboratory) found high-amplitude (>20%) quasi-periodic oscillations (QPO) with periods of 7-10 seconds in the count rate in the EUVE Deep Survey data from both the 1993 August and 1994 June outbursts of the cataclysmic variable SS Cygni. These QPOs have been known about for some time from HEAO-1 and EXOSAT studies, but no other mission has had such extensive coverage of the oscillations, or has been able to track the evolution of the period, phase, and amplitude of the oscilations as a function of time/outburst phase/etc. A precise knowledge of the properties of the oscillations is crucial to understand the nature, the size, and the mechanisms at work in the emitting region. Dr. Mauche is investigating the presence of QPOs also in the VW Hyi DS data:
Dear EUV aficionados: Enclosed below is a postscript file of a figure showing the EUVE DS light curve of the dwarf nova SS Cyg during the rise and plateau stages of its 1994 June/July outburst. I believe that the most interesting aspect of the light curve is the extraordinarily fast rise of the EUV flux: ~2.3 orders of magnitude increase in the count rate in ~ 6 hrs or 4 satellite orbits. For this outburst, the optical light came up ~ 1 day before the EUV light. This delay was ~3 days for the anomolous 1993 August outburst. Warning: use this figure with caution. It is very preliminary. The small dots on the figure shows the level of the (scaled) background for comparison. Chris Mauche
Figure (28 Kb post-script): EUVE DS light curve of SS Cyg during 1994 June/July outburst