Related papers: Truncated accretion discs in black hole X-ray bina…
This is an introduction to models of accretion discs around black holes. After a presentation of the non-relativistic equations describing the structure and evolution of geometrically thin accretion discs we discuss their steady-state…
Theoretical models of accretion discs and observational data indicate that the X-ray emission from the inner parts of an accretion disc can irradiate its outer regions and induce a thermal wind, which carries away the mass and angular…
We report on simulations in general relativity of magnetized disks onto black hole binaries. We vary the binary mass ratio from 1:1 to 1:10 and evolve the systems when they orbit near the binary-disk decoupling radius. We compare (surface)…
We investigate the time evolution of sub-Keplerian transonic accretion flow onto a non-rotating black hole using axisymmetric viscous hydrodynamic simulations. We simulate the accretion flow using boundary values from semi-analytical…
X-rays are a critical wavelength for understanding supermassive black holes (SMBHs). X-rays probe the inner accretion flow, closest to the event horizon, where gas inspirals, releasing energy and driving black hole growth. This region also…
The key aspect of the very successful truncated disc model for the low/hard X-ray spectral state in black hole binaries is that the geometrically thin disc recedes back from the last stable orbit at the transition to this state. This has…
Accretion discs around black holes in X-ray binary stars are warped if the spin axis of the black hole is not perpendicular to the binary orbital plane. They can also become eccentric through an instability involving a resonance with the…
The activity of at least one repeating Fast Radio Burst (FRB) source is periodically modulated. If this modulation is the result of precession of the rotation axis and throat of an accretion disc around a black hole, driven by a companion…
Observations of black hole binaries (BHBs) have established a rich phenomenology of X-ray states. The soft states range from the low variability, accretion disc dominated thermal state (TD) to the higher variability, non-thermal steep power…
The inner radius of the accretion disc around a black hole in the low/hard state can be measured in one of two ways. Firstly, via the extent of broadening of the iron emission line, and secondly, from the luminosity and temperature of the…
X-ray binaries (XRBs) display spectral state transitions that are accompanied by substantial changes in the hardness, luminosity, and structure of the accretion flow. We developed a GPU-accelerated cooling toolkit for general relativistic…
We investigate the effects of the Gauss-Bonnet (GB) gravitational trace anomaly on the circular motion of test particles around black holes (BHs) and its implications for quasi-periodic oscillations (QPOs) in various theoretical models.…
While nobody would deny the presence of Quasi-Periodic Oscillations in the power density spectrum of Black hole binaries nor their importance in the understanding of the mechanisms powering the X-ray emissions, the possible impact on the…
Accretion discs are present around both stellar-mass black holes in X-ray binaries and supermassive black holes in active galactic nuclei. A wide variety of circumstantial evidence implies that many of these discs are warped. The standard…
There are many simplifications in current relativistic reflection models and this introduces systematic uncertainties in the measurement of the properties of the source. In this paper, we study the impact of the radiation crossing the…
The nature of accretion onto stellar mass black holes in the low/hard state remains unresolved, with some evidence suggesting that the inner accretion disc is truncated and replaced by a hot flow. However, the detection of relativistic…
In this paper we continue the first ever study of magnetized mini-disks coupled to circumbinary accretion in a supermassive binary black hole (SMBBH) approaching merger reported in Bowen et al. 2018. We extend this simulation from 3 to 12…
Although quasi-periodic oscillations (QPOs) have been discovered in different X-ray sources, their origin is still a matter of debate. Analytical studies of hydrodynamic accretion disks have shown three types of trapped global modes with…
Recent observations of two black hole candidates (GX 339-4 and J1753.5-0127) in the low-hard state (L_X/L_Edd ~ 0.003-0.05) suggest the presence of a cool accretion disk very close to the innermost stable orbit of the black hole. This runs…
The study of a disturbed accretion disk holds great significance in the realm of astrophysics, as such events play a crucial role in revealing the nature of disk structure, the release of energy, and the generation of shock waves.…