Can Lense–Thirring Precession Produce QPOs in Supersonic Accretion Flows?

Abstract The timing properties of X-ray binaries are still not understood, particularly the presence of quasi-periodic oscillations (QPOs) in their X-ray power spectra. The solid-body regime of Lense–Thirring precession is one prominent model invoked to explain the most common type of QPOs, Type C. However, solid-body precession requires a specific structure that has not been examined in light of constrained properties of accretion flows. We assume in this paper, as solid-body precession requires, a disk separated into two flows at a transition radius r t : a cold outer flow and a hot inner flow (playing the role of the corona). We explore the physical structure of both flows using model-independent estimates of accretion parameters. We show that, in order to reproduce the observed X-ray spectra during luminous hard states, the hot flow must accrete at sonic to supersonic speeds, unreachable with typical viscous torques. As a result of this extreme accretion speed (or high α parameter), no region of the disk during these states lies in the “wave-like” regime required for solid-body precession. Furthermore, we expect the flow to align with the black hole spin axis via the Bardeen–Petterson effect inside a radius r break > r t . As a consequence, the hot inner flow cannot exhibit solid body precession—as currently pictured in the literature—during luminous hard states. Since Type C QPOs are prevalent in these states, we conclude that this mechanism is unlikely to be responsible for producing Type C QPOs around stellar mass black holes.

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