The model constraints from the observed trends for the quasi-periodic oscillation in RE J1034+396

TL;DR

This paper investigates the variability of X-ray quasi-periodic oscillations in RE J1034+396, revealing a correlation between QPO frequency and flux that constrains theoretical models, favoring linear structures over hot spot models.

Contribution

It provides the first detailed analysis of QPO frequency drift and its correlation with flux, offering new constraints on QPO models in active galactic nuclei.

Findings

QPO frequency drifts over time.

QPO frequency correlates with X-ray flux with a short delay.

Excludes hot spot orbiting models, favors linear structures.

Abstract

We analyze the time variability of the X-ray emission of RE J1034+396 -- an active galactic nucleus with the first firm detection of a quasi-periodic oscillations (QPO). Based on the results of a wavelet analysis, we find a drift in the QPO central frequency. The change in the QPO frequency correlates with the change in the X-ray flux with a short time delay. The data specifically suggest a linear dependence between the QPO period and the flux, and this gives important constraints on the QPO models. In particular, it excludes explanation in terms of the orbiting hot spot model close to a black hole. Linear structures such as shocks, spiral waves, or very distant flares are favored.