Physical origin of low-frequency quasi-periodic oscillations

Determine the physical origin of low-frequency quasi-periodic oscillations in black-hole X-ray binaries, including the mechanisms responsible for their observed timing and energy-dependent properties.

Background

Low-frequency quasi-periodic oscillations are commonly observed in black-hole X-ray binaries and are thought to probe processes occurring near the black hole. The paper notes that, despite extensive observational and theoretical work, no consensus has been reached regarding their physical origin. Proposed explanations include geometric mechanisms such as Lense–Thirring precession, transition-layer oscillations, shock oscillations, and variability of the Comptonizing region.

References

Despite extensive observational and theoretical efforts, the physical origin of LFQPOs remains unclear.

— Complex Energy-Dependent Behaviour of Quasi-Periodic Oscillation Observed in GRS 1915+105  (2608.13068 - Sharma et al., 13 Aug 2026) in Section 1, Introduction

The disappearance of the QPO has been observed for decades, but the underlying physical mechanism remains unclear.

— Investigating the disappearance of a type-C QPO in black hole X-ray binary Swift J151857-572147 with AstroSat  (2608.26627 - Ram et al., 27 Aug 2026) in Section 1, Introduction; Section 4.2, Discussion, “Disappearance of the QPO and the low-frequency bump”