Iron Line Variability of Discoseismic Corrugation Modes

TL;DR

This paper investigates how discoseismic corrugation modes in accretion disks around black holes cause variability in relativistically broadened iron lines, potentially explaining low-frequency QPOs and constraining black hole spins.

Contribution

It introduces a semi-analytic raytracing method to model iron line variability caused by discoseismic oscillations, linking spectral features to black hole properties.

Findings

Corrugation mode frequencies match observed LFQPOs for low spins.

Iron line variability can be used to confirm discoseismic models.

Potential to constrain black hole spin with spectral observations.

Abstract

Using a fast semi-analytic raytracing code, we study the variability of relativistically broadened iron lines due to discoseismic oscillations concentrated in the inner-most regions of accretion discs around black holes. The corrugation mode, or c-mode, is of particular interest as its natural frequency corresponds well to the ~0.1-15Hz range observed for low-frequency quasi-periodic oscillations (LFQPOs) for lower spins. Comparison of the oscillation phase dependent variability and QPO-phase stacked iron line observations will allow such discoseismic models to be confirmed or ruled out as a source of particular LFQPOs. The spectral range and frequency of the variability of the iron line due to corrugation modes can also potentially be used to constrain the black hole spin if observed with sufficient temporal and spectral resolution.