The X-ray binary analogy to the first AGN quasi-periodic oscillation

The narrow line Seyfert 1 galaxy REJ 1034+396 is so far unique amongst active galaxies (AGN) in showing a quasi-periodic oscillation (QPO) in its variability power spectrum. There are multiple types of QPO seen in black hole binary (BHB) systems, so we need to identify which BHB QPO corresponds to the one seen in the AGN. A key hint is the `hot disc dominated' energy spectrum of REJ 1034+396 which is sufficiently unusual that it suggests a mildly super-Eddington flow, also favoured by the most recent mass estimates for the AGN. This suggests the 67 Hz QPO seen occasionally in the mildly super-Eddington BHB GRS 1915+105 as the most likely counterpart, assuming mass scaling of the QPO frequency. This is supported by the fact that these data from GRS 1915+105 have an energy spectrum which is also dominated by a `hot disc' component. Here we show that the underlying broad band power spectral shape and normalization are also similar, providing further consistency checks for this identification. Thus the AGN QPO adds to the growing evidence for a simple mass scaling of the accretion flow properties between stellar and supermassive black holes.