Related papers: Diskoseismology and QPOs Confront Black Hole Spin
We have identified the presence of large-scale, low-frequency dynamo cycles in a long-duration, global, magnetohydrodynamic (MHD) simulation of black hole accretion. Such cycles had been seen previously in local shearing box simulations,…
Aperiodic variability and Quasi Periodic Oscillations (QPOs) are observed from accretion disks orbiting white dwarfs, neutron stars, and black holes, suggesting that the flow is universally broken up into discrete blobs. We consider the…
High frequency quasi-periodic oscillations (HF QPOs) are observed in the X-ray power-density spectra (PDS) of several microquasars and low mass X-ray binaries. Many proposed QPO models are based on oscillations of accretion toroidal fluid…
In this study, the behavior of high-frequency quasi-periodic oscillations (QPOs) is investigated around a Kerr black hole immersed in a uniform Bertotti-Robinson magnetic field. The motion of the test particle is analyzed by determining the…
Using a generalized non-spherical, multi-transonic accretion flow model, we analytically calculate the normalized QPO frequency ${\bar {\bf {\nu}}}_{qpo}$ of galactic black hole candidates in terms of dynamical flow variables and…
A typical galaxy is thought to contain tens of millions of stellar-mass black holes, the collapsed remnants of once massive stars, and a single nuclear supermassive black hole. Both classes of black holes accrete gas from their…
Most quasars are known to be radio quiet and according to the ``spin paradigm'', which connects their radio-loudness with the value of the black hole spin, they must harbor very slowly rotating black holes. On the other hand, quasars are…
The black hole mass and spin estimates assuming various specific models of the 3:2 high frequency quasi-periodic oscillations (HF QPOs) have been carried out in Torok et al. (2005, 2011). Here we briefly summarize some current points.…
We show that a luminous torus in the Schwarzschild metric oscillating along its own axis gives rise to a periodically varying flux of radiation, even though the source of radiation is steady and perfectly axisymmetric. This implies that the…
The variability of X-rays observed from accreting black hole systems, including quasi-periodic oscillations (QPOs), suggests a complex nonlinear dynamics in the corona. Here, we propose a new theoretical framework for this problem, based on…
This paper investigates the high frequency quasi-periodic oscillations (HFQPOs) phenomenon around the black bounce-type (BBT) spacetime using the resonance models. We calculated the location of the innermost stable circular orbit (ISCO) for…
We present a theoretical model for the alternating phase lags associated with QPO fundamental and harmonic frequencies observed in some Galactic black-hole candidates. We assume that the accretion flow exhibits a transition from an outer…
A recent measurement of double peak QPOs frequencies in Sgr A* is consistent with the 3:2 ratio. The same ratio is firmly established by previous observations in all double peak kHz QPOs in microquasars and theoretically explained by…
A model of low-frequency quasi-periodic oscillations (LFQPOs) of black hole X-ray binaries (BHXBs) is proposed based on the perturbed magnetohydrodynamic (MHD) equations of accretion disk. It turns out that the LFQPOs frequencies of some…
Accreting stellar-mass black holes often show a `Type-C' quasi-periodic oscillation (QPO) in their X-ray flux, and an iron emission line in their X-ray spectrum. The iron line is generated through continuum photons reflecting off the…
The rather elusive High-Frequency Quasi-Periodic Oscillations(HFQPO) observed in the X-ray lightcurve of black holes have been seen in a wide range of frequencies, even within one source. It is also notable to have been detected in "pairs"…
The presence of a kHz frequency in LMXBs has been expected from scaling laws, by analogy with the QPO phenomenon in HMXB X-ray pulsars. Interpretation of the two kHz frequencies, observed in accreting neutron stars, in terms of non-linear…
Quasiperiodic oscillations (QPOs) have been observed in the power-density spectra of some low-mass X-ray binaries(LMXB) containing a black hole. The two major groups of QPOs -- low-frequency and high-frequency -- have rather different…
{This study explores the motion of massive test particles and associated quasi-periodic oscillations (QPOs) around an accelerating black hole. The acceleration factor $A$ suppresses the radial effective potential $V_{\text{eff}}$, thereby…
If binary black holes form following the successive core collapses of sufficiently massive binary stars, precessional dynamics may align their spins $\mathbf S_1$ and $\mathbf S_2$ and the orbital angular momentum $\mathbf L$ into a plane…