Hydrodynamic simulations of viscous accretion flows around black holes

Giri, Kinsuk; Chakrabarti, Sandip K.

doi:10.1111/j.1365-2966.2011.20343.x

Cited by 7 publications

(1 citation statement)

References 32 publications

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“…This causes a sudden rise of temperature which puffs up the matter creating a hotter region known as CENBOL which is responsible for the inverse Comptonization of the soft photons generated by the Keplerian disk. Using hydrodynamic simulations (see [34] and [35]), one finds self-consistent outflows are being produced from the post-shock region. In our model, the QPOs are generated due to the shock oscillation at the CENBOL boundary.…”

Section: Discussionmentioning

confidence: 99%

Discovery of Jet-Induced Soft Lags of XTE J1550-564 during Its 1998 Outburst †

Chatterjee

Dutta²,

Patra

et al. 2019

Recent Progress in Relativistic Astrophysics

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X-ray time lags are complicated in nature. The exact reasons for complex lag spectra are yet to be known. However, the hard lags, in general are believed to be originated due to inverse Comptonization process. But, the origin of soft lags remained mischievous. Recent studies on "Disk-Jet Connections" revealed that the jets are also contributing in the X-ray spectral and timing properties in a magnitude which was more than what was predicted earlier. In this article, we first show an exact anti-correlation between X-ray time lag and radio flux for XTE J1550-546 during its 1998 outburst. We propose that the soft lags might be generated due to the change in the accretion disk structure along the line of sight during higher jet activity.

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Section: Discussionmentioning

confidence: 99%

Discovery of Jet-Induced Soft Lags of XTE J1550-564 during Its 1998 Outburst †

Chatterjee

Dutta²,

Patra

et al. 2019

Recent Progress in Relativistic Astrophysics

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Effects of turbulent viscosity on a rotating gas ring around a black hole: Results of numerical simulations

Giri

Chang

2015

Astron Nachr

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In this paper, we present the time evolution of a rotationally axisymmetric gas ring around a non rotating black hole using two dimensional grid-based hydrodynamic simulation. We show the way in which angular momentum transport is included in simulations of non-self-gravitating accretion of matter towards a black hole. We use the Shakura-Sunyaev α viscosity prescription to estimate the turbulent viscosity for all major viscous stress tensors. We investigate how a gas ring which is initially assumed to rotate with Keplerian angular velocity is accreted on to a black hole and hence forms accretion disc in the presence of turbulent viscosity. We show that the centrifugal pressure supported sub-Keplerian flow with shocks forms when the ring starts to disperse with inclusion of relatively small amount of viscosity. But, if the viscosity is above the critical value, the shock disappears altogether and the whole disc becomes Kepleiran which is subsonic everywhere except in a region close to the horizon, where it supersonically enters to the black hole. We discovered a multiple valued Mach number solution and the corresponding density distributions that connects matter (a) from the initial Keplerian gas ring to a sub-Keplerian disc with shocks in presence of small amount of viscosity and (b) from the sub-Keplerian flow to a Keplerian disc in presence of huge amount of viscosity. We calculate the temporal variations of the magnitude of various time scales which ensure us about the stability of the flow.

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Properties of relativistic hot accretion flow around a rotating black hole with radially varying viscosity

Singh,

Das

2024

Astrophys Space Sci

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We examine the effect of variable viscosity parameter (α) in relativistic, low angular momentum advective accretion flow around rotating black holes. Following the recent simulation studies of magnetohydrodynamic disk that reveal the radial variation of α(r), we theoretically investigate the properties of the global transonic accretion flow considering a one-dimensional power law prescription of viscosity parameter as α(r) ∝ r θ , where the viscosity exponent θ is a constant. In doing so, we adopt the relativistic equation of state and solve the fluid equations that govern the flow motion inside the disk. We find that depending on the flow parameters, accretion flow experiences centrifugally supported shock transition and such shocked accretion solutions continue to exist for wide ranges of the flow energy, angular momentum, accretion rate and viscosity exponent, respectively. Due to shock compression, the hot and dense post-shock flow (hereafter PSC) can produce the high energy radiations after reprocessing the soft photons from the pre-shock flow via inverse Comptonization. Since PSC is usually described using shock radius (rs), compression ratio (R) and shock strength (S), we study the role of θ in deciding rs, R and S, respectively. Moreover, we obtain the parameter space for shock and find that possibility of shock formation diminishes as θ is increased. Finally, we compute the limiting value of θ (i.e., θ max ) that admits shock and find that flow can sustain more viscosity when it accretes onto rapidly rotating (ak → 1) black hole in comparison to weakly rotating (ak → 0) black hole.

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Hydrodynamic simulations of viscous accretion flows around black holes

Cited by 7 publications

References 32 publications

Discovery of Jet-Induced Soft Lags of XTE J1550-564 during Its 1998 Outburst †

Discovery of Jet-Induced Soft Lags of XTE J1550-564 during Its 1998 Outburst †

Effects of turbulent viscosity on a rotating gas ring around a black hole: Results of numerical simulations

Properties of relativistic hot accretion flow around a rotating black hole with radially varying viscosity

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