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arXiv · 2210.02944

Effect of geometrically thin discs on precessing, thick flows: Relevance to type-C QPOs

D. A. Bollimpalli·P. C. Fragile·W. Kluźniak
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Abstract

Type-C quasi-periodic oscillations (QPOs) are the low-frequency QPOs most commonly observed during the hard spectral state of X-ray binary systems. The leading model for these QPOs is the Lense-Thirring precession of a hot, geometrically thick accretion flow that is misaligned with respect to the black hole spin axis. However, none of the work done to date has accounted for the effects of a surrounding, geometrically thin disc on this precession, as would be the case in the truncated disc picture of the hard state. To address this, we perform a set of GRMHD simulations of truncated discs misaligned with the spin axes of their central black holes. Our results confirm that the inner-hot flow still undergoes precession, though at a rate that is only 5 percent of what is predicted for an isolated, precessing torus. We find that the exchange of angular momentum between the outer, thin and the inner, thick disc causes this slow-down in the precession rate and discuss its relevance to type-C QPOs.

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D. A. Bollimpalli, P. C. Fragile, W. Kluźniak. 2022-10-06. Effect of geometrically thin discs on precessing, thick flows: Relevance to type-C QPOs. https://doi.org/10.1093/mnrasl%2Fslac155

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