Quasi‐periodic oscillations are more than timing features: Applying the accretion‐ejection instability in super massive black‐holes

Low frequency quasi-periodic oscillations (LFQPOs) have always been seen uniquely as a timing feature, with most models focused on reproducing only their timing behavior. Previously, the accretion-ejection instability (AEI) predicted the existence of a more subtle effect on their energy spectrum. In the case of low mass X-ray binaries (LMXB), that effect was deemed impossible to detect. Although the AEI can be naturally expanded to higher-mass systems, there was no observational drive to do it until now. However, the several (candidate) QPOs detected in supermassive black hole sources in the last decade, now seems the right moment to explore the applicability of the AEI model. Using our numerical observatory, we compute the different observables for a system with the AEI active and we take advantage of the longer timescale coming from the higher mass system, to see if the effect on the energy spectrum hinted at in LMXB, could become detectable. After confirming that the AEI causes an imprint of the QPO on the energy spectrum that should reach detectable levels in SMBH, we turned to observations of 2XMM J123103.2 and performed a proof of concept spectro-timing fit of the QPO pulse profile simultaneously with how its energy spectrum changes along it. While the limited 2XMM J123103.2 data showed the predicted effect at only 1.7 sigma$$ 1.7\sigma $$, it is fully consistent with the AEI model and hence worthy of further investigation in other systems.