Confrontation of Observation and Theory: High Frequency QPOs in X-ray Binaries, Tidal Disruption Events, and Active Galactic Nuclei

TL;DR

This paper analyzes high-frequency QPOs across different black hole systems, revealing that current models explain stellar black hole oscillations but not those in supermassive black holes or AGN, indicating a need for more comprehensive theories.

Contribution

It provides a comparative analysis of QPO observations across black hole types and evaluates the applicability of existing theoretical models, highlighting gaps in understanding for supermassive black holes and AGN.

Findings

Supermassive black holes occupy a distinct parameter space from stellar black holes.

QPOs in tidal disruption events align with ISCO frequencies.

QPOs in AGN are not explained by current models.

Abstract

We compile observations of high-frequency quasi-periodic oscillations (QPOs) around black holes, both stellar and supermassive, and compare their positions in the parameter space of black hole mass, spin, and oscillation frequency. We find that supermassive black holes occupy a separate region of parameter space than stellar, and further, that QPOs seen around tidal disruption events rather than Seyfert-type AGN occupy an entirely different space. We then compare these results to the orbital resonance, diskoseismic, warped disk, and disk-jet coupling theoretical models for the origin of high-frequency QPOs. We find that while oscillations around stellar mass black holes are generally consistent with the above models, supermassive black holes are decidedly not. Oscillations seen in tidal disruption events are consistent with oscillations near the frequency of the innermost stable circular orbit (ISCO), while QPOs in AGN are not accounted for by any of the physical models in consideration. This indicates that despite the scale invariance of accretion processes implied by a decades-wide correlation between QPO frequency and black hole mass, any theory of high frequency QPOs must relate the frequency to more than just the mass and spin.