Modeling the time-resolved quasi-periodic oscillations in AGNs

TL;DR

This paper models the time-resolved QPOs in AGNs, specifically in RE J1034+396, using shock oscillations in hot accretion flows, constraining the physical mechanisms behind observed period-luminosity correlations.

Contribution

It introduces a shock oscillation model in hot accretion flows that explains the observed QPO period drift and flux variations in AGNs, incorporating general relativistic effects and black hole spin.

Findings

Shock location variations match observed QPO period and flux changes.

Flow angular momentum perturbations explain the period-luminosity correlation.

Flow energy perturbations produce too strong flux responses.

Abstract

Observation of the bright Seyfert 1 galaxy RE J1034+396 is believed to demonstrate a drift of 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 black hole accretion disc, that modeling 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 (AGN). 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, 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 flux response to the change of 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 similar quantitative study for other QPO scenarios will be necessary.