Mapping quasi-periodic oscillations from the outbursting intermediate   polar GK Persei
  We present time-resolved spectrophotometry of GK Per taken on the rise to outburst maximum, in which we detect 5000 s QPOs in the optical emission lines. We use this opportunity to provide a kinematically-resolved analysis of the phenomenon. Observations are consistent with reprocessing off blobs of gas orbiting within the inner accretion disc, and evidence is found for the migration of the QPO source towards the compact star over orbital timescales. 
L. Morales-Rueda, M. D. Still, P. Roche