Quasi periodic oscillations in active galactic nuclei

Understand

Quasi-periodic oscillations (QPOs) are coherent peaks of variability power observed in the X-ray power spectra (PSDs) of stellar mass X-ray binaries (XRBs).

• A scale invariance of the accretion process implies they should be present in the active galactic nuclei.
• The first robust detection was a $\sim 1$ hr periodicity in the Seyfert galaxy RE J1034+396 from a $\sim 90$ ks XMM-Newton observation, however, subsequent observations failed to detect the QPO in the $0.3-10.0$ keV band.
• In this talk we present the recent detection of the $\sim 1$ hr periodicity in the $1.0-4.0$ keV band of 4 further low-flux/spectrally-harder observations of RE J1034+396 (see Alston et al 2014).