Speaker: Gibwa Musoke (University of Amsterdam)

Date: Thursday 23 March 2023

Time: 14:00

Location: Physics 3.27

Triggering Quasi-Periodic Oscillations by Tearing Accretion Disks

Black hole X-ray binaries (BHXRBs) display a wide range of variability phenomena, from large-scale spectral state changes to broadband variability and quasi periodic oscillations (QPOs), however the physical mechanisms driving this variability are not well understood. QPOs can be used as a powerful diagnostic tool of black hole accretion and evolution, provided that the mechanism responsible for their production is known. However, to-date there is no general consensus on the origin of QPOs. An attractive mechanism for QPO production is disk tearing in tilted accretion flows, in which the disk tears apart forming independently precessing sub-disks, the emission from which is expected to be quasi-periodic.

In this talk I discuss the first discovery of HFQPOs in a general relativistic magnetohydrodynamic simulation of a highly tilted, geometrically thin accretion disk. The HFQPOs are triggered in close proximity to the location of disk tearing, supporting the view that disk tearing can generate HFQPOs. I will also discuss the mechanisms by which low-frequency QPOs can be produced in this model, in order to highlight how disk tearing can be a unified model for QPO production.