The 1996 dwarf nova outburst of the intermediate polar GK Persei

GK Persei is an intermediate polar that exhibits a dwarf nova outburst approximately every 1000 days. During previous outbursts the system has displayed kilo-second quasi-periodic oscillations (QPOs) in X-ray emission. These oscillations are unique in that they are an order of magnitude longer than QPOs usually observed in disc-fed cataclysmic variables. We have detected the optical counterpart of these QPOs in spectrophotometry collected during the 1996 outburst. The presence of these QPOs in Doppler-broadened emission lines originating from the highly-supersonic accretion flow enables us to place useful constraints on the location of the QPO source and its formation mechanism.