Effect of turbulent pressure on the origin of low-frequency quasi-periodic oscillations in rotating black holes

Abstract

ABSTRACT Quasi-periodic oscillation (QPO), particularly of low frequency (LF), is a very obvious feature of outbursting black hole candidates. The association of QPOs in a specific spectral state and their transition with states make them a key ingredient in understanding the underlying physical processes that produce them. Observations have revealed that generally, in the hard spectral state of the outburst, the size of the Compton cloud is relatively bigger, which produces low-frequency QPOs (LFQPOs). In progressive days increased cooling shrinks the area of the cloud, the inner edge of the disc comes close to the black holes, and produces higher frequency QPOs. However, rotating black holes with higher spin values are likely to produce LFQPOs even if their inner edge of the disc is closer to the hole. Here, for the first time, we address the issue, solving hydrodynamic flow equations in the presence of qualitative turbulent pressure and cooling in pseudo-Kerr geometry. Increasing turbulence slackens the infalling flow, thus the infall time becomes longer, producing LFQPOs. Our study discovers that the effect of turbulence modifies LFQPOs value significantly, by a factor of a few lower throughout the angular momentum distribution of the flow. We find a strong correlation between the turbulence and the spin parameter of the hole. Finally, we discuss the observed results in light of the present solution.