2011MNRAS.414..627D

The observation of the bright Seyfert 1 galaxy RE J1034+396 is believed to demonstrate a drift in the central period of the quasi-periodic oscillation (QPO) linearly correlated with the temporary X-ray luminosity. We show, using a specific scenario of the oscillation mechanism in a black hole accretion disc, that modelling such correlated trends puts very strong constraints on the nature of this oscillation and the characteristic features of the hot flow in active galactic nuclei. In our model, QPO oscillations are due to the oscillations of the shock formed in the low angular momentum hot accretion flow, and the variation of the shock location corresponds to the observed changes in the QPO period and the X-ray flux. In this scenario, a change in the shock location caused by perturbation of the flow angular momentum is compatible with the trends observed in RE J1034+396, whereas the perturbation of the specific flow energy results in too strong a flux response to the change in the oscillation period. Using a complete general relativistic framework to study the accretion flow in the Kerr metric, we discuss the role of the black hole spin in the period drift. Future missions are expected to bring more active galaxies with time-resolved quasi-periodic oscillations, so a similar quantitative study for other QPO scenarios will be necessary.