Evolution of Shock Structures and QPOs After Halting BHL Accretion onto Kerr Black Hole

Abstract

In this paper, we investigate for the first time the quasi-periodic oscillations (QPOs) that arise as a result of halting the Bondi-Hoyle-Lyttleton (BHL) accretion mechanism around a Kerr black hole. Unlike previous studies, which focused on shock cones or perturbed tori, we show that stopping BHL accretion leads to the formation of a new plasma structure. On this plasma structure, spiral shock waves are observed to develop. These shock waves are found to excite both low-frequency (LFQPOs) and high-frequency QPOs (HFQPOs). Two key results emerge from our numerical simulations. First, LFQPOs arise only when the halted flow is supersonic, identifying for the first time the velocity dependence of their formation. Second, nonlinear couplings that produce $3:2$, $2:1$, and $1:2:3$ resonances appear exclusively for rapidly rotating black holes ($a/M = 0.9$), directly linking spin to resonance states. In addition, it is demonstrated that HFQPOs are strongly influenced by the black hole spin. The generated QPOs are observed to be excited through the modes induced by the black hole spacetime curvature. The frequencies obtained from the numerical simulations align with observations of $GRS1915+105$, $XTEJ1550-564$, and $REJ1034+396$, thereby bridging stellar-mass and supermassive black hole systems within a unified framework. Thus, the newly uncovered physical mechanism associated with halted BHL accretion is capable of explaining both the persistence and the intermittency of QPOs across diverse astrophysical environments.