Disc Tearing and Bardeen-Petterson Alignment in GRMHD Simulations of Highly Tilted Thin Accretion Discs

Abstract Luminous active galactic nuclei (AGN) and X-Ray binaries (XRBs) often contain geometrically thin, radiatively cooled accretion discs. According to theory, these are – in many cases – initially highly misaligned with the black hole equator. In this work, we present the first general relativistic magnetohydrodynamic simulations of very thin (h/r∼0.015-0.05) accretion discs around rapidly spinning (a∼0.9) black holes and tilted by 45-65 degrees. We show that the inner regions of the discs with h/r≲0.03 align with the black hole equator, though out to smaller radii than predicted by analytic work. The inner aligned and outer misaligned disc regions are separated by a sharp break in tilt angle accompanied by a sharp drop in density. We find that frame-dragging by the spinning black hole overpowers the disc viscosity, which is self-consistently produced by magnetized turbulence, tearing the disc apart and forming a rapidly precessing inner sub-disc surrounded by a slowly precessing outer sub-disc. We find that the system produces a pair of relativistic jets for all initial tilt values. At small distances the black hole launched jets precess rapidly together with the inner sub-disc, whereas at large distances they partially align with the outer sub-disc and precess more slowly. If the tearing radius can be modeled accurately in future work, emission model independent measurements of black hole spin based on precession-driven quasi-periodic oscillations may become possible.

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Strongly magnetized accretion discs: structure and accretion from global magnetohydrodynamic simulations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3572 ◽

2019 ◽

Vol 492 (2) ◽

pp. 1855-1868 ◽

Cited By ~ 11

Author(s):

Bhupendra Mishra ◽

Mitchell C Begelman ◽

Philip J Armitage ◽

Jacob B Simon

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Galactic Nuclei ◽

Magnetic Pressure ◽

Accretion Discs ◽

Surface Layers ◽

Large Scale Magnetic Field ◽

Net Flux ◽

Magnetohydrodynamic Simulations ◽

X Ray Binaries

ABSTRACT We use global magnetohydrodynamic simulations to study the influence of net vertical magnetic fields on the structure of geometrically thin (H/r ≈ 0.05) accretion discs in the Newtonian limit. We consider initial mid-plane gas to magnetic pressure ratios $\beta _0 = 1000,\, 300$, and 100, spanning the transition between weakly and strongly magnetized accretion regimes. We find that magnetic pressure is important for the discs’ vertical structure in all three cases, with accretion occurring at $z$/R ≈ 0.2 in the two most strongly magnetized models. The disc mid-plane shows outflow rather than accretion. Accretion through the surface layers is driven mainly by stress due to coherent large-scale magnetic field rather than by turbulent stress. Equivalent viscosity parameters measured from our simulations show similar dependencies on initial β0 to those seen in shearing box simulations, though the disc mid-plane is not magnetic pressure dominated even for the strongest magnetic field case. Winds are present but are not the dominant driver of disc evolution. Over the (limited) duration of our simulations, we find evidence that the net flux attains a quasi-steady state at levels that can stably maintain a strongly magnetized disc. We suggest that geometrically thin accretion discs in observed systems may commonly exist in a magnetically ‘elevated’ state, characterized by non-zero but modest vertical magnetic fluxes, with potentially important implications for disc phenomenology in X-ray binaries and active galactic nuclei.

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On different types of instabilities in black hole accretion discs: implications for X-ray binaries and active galactic nuclei

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2011.18544.x ◽

2011 ◽

Vol 414 (3) ◽

pp. 2186-2194 ◽

Cited By ~ 41

Author(s):

Agnieszka Janiuk ◽

Bożena Czerny

Keyword(s):

Black Hole ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Accretion Discs ◽

X Ray ◽

Black Hole Accretion ◽

Different Types ◽

X Ray Binaries ◽

Hole Accretion

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Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab784 ◽

2021 ◽

Vol 503 (3) ◽

pp. 4563-4575

Author(s):

A Jiménez-Rosales ◽

J Dexter ◽

S M Ressler ◽

A Tchekhovskoy ◽

M Bauböck ◽

...

Keyword(s):

Black Hole ◽

Relativistic Effects ◽

Image Features ◽

Black Hole Mass ◽

Magnetic Turbulence ◽

Intensity Images ◽

General Relativistic ◽

Sharp Image ◽

Sgr A ◽

Magnetohydrodynamic Simulations

ABSTRACT Using general relativistic magnetohydrodynamic simulations of accreting black holes, we show that a suitable subtraction of the linear polarization per pixel from total intensity images can enhance the photon ring feature. We find that the photon ring is typically a factor of ≃2 less polarized than the rest of the image. This is due to a combination of plasma and general relativistic effects, as well as magnetic turbulence. When there are no other persistently depolarized image features, adding the subtracted residuals over time results in a sharp image of the photon ring. We show that the method works well for sample, viable GRMHD models of Sgr A* and M87*, where measurements of the photon ring properties would provide new measurements of black hole mass and spin, and potentially allow for tests of the ‘no-hair’ theorem of general relativity.

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Radiative efficiency of hot accretion flow and the radio/X-ray correlation in X-ray binaries

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315007723 ◽

2014 ◽

Vol 10 (S312) ◽

pp. 139-140

Author(s):

Fu-Guo Xie

Keyword(s):

Black Hole ◽

Active Galactic Nuclei ◽

Accretion Rate ◽

Galactic Nuclei ◽

X Ray ◽

Radiative Efficiency ◽

Accretion Flow ◽

Accretion Rates ◽

Distinctive Property ◽

X Ray Binaries

AbstractSignificant progresses have been made since the discovery of hot accretion flow, a theory successfully applied to the low-luminosity active galactic nuclei (LLAGNs) and black hole (BH) X-ray binaries (BHBs) in their hard states. Motivated by these updates, we re-investigate the radiative efficiency of hot accretion flow. We find that, the brightest regime of hot accretion flow shows a distinctive property, i.e. it has a constant efficiency independent of accretion rates, similar to the standard thin disk. For less bright regime, the efficiency has a steep positive correlation with the accretion rate, while for faint regime typical of advection-dominated accretion flow, the correlation is shadower. This result can naturally explain the observed two distinctive correlations between radio and X-ray luminosities in black hole X-ray binaries. The key difference in systems with distinctive correlations could be the viscous parameter, which determines the critical luminosity of different accretion modes.

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Dynamical Evolution of Accretion Flow onto a Black Hole

Symposium - International Astronomical Union ◽

10.1017/s0074180900116006 ◽

1998 ◽

Vol 188 ◽

pp. 455-456

Author(s):

M. Yokosawa

Keyword(s):

Black Hole ◽

Active Galactic Nuclei ◽

Event Horizon ◽

Accretion Disk ◽

Dynamical Evolution ◽

Galactic Nuclei ◽

Thick Disk ◽

X Ray ◽

General Relativistic ◽

Inner Region

Active galactic nuclei(AGN) produce many type of active phenomena, powerful X-ray emission, UV hump, narrow beam ejection, gamma-ray emission. Energy of these phenomena is thought to be brought out binding energy between a black hole and surrounding matter. What condition around a black hole produces many type of active phenomena? We investigated dynamical evolution of accretion flow onto a black hole by using a general-relativistic, hydrodynamic code which contains a viscosity based on the alpha-model. We find three types of flow's pattern, depending on thickness of accretion disk. In a case of the thin disk with a thickness less than the radius of the event horizon at the vicinity of a marginally stable orbit, the accreting flow through a surface of the marginally stable orbit becomes thinner due to additional cooling caused by a general-relativistic Roche-lobe overflow and horizontal advection of heat. An accretion disk with a middle thickness, 2rh≤h≤ 3rh, divides into two flows: the upper region of the accreting flow expands into the atmosphere of the black hole, and the inner region of the flow becomes thinner, smoothly accreting onto the black hole. The expansion of the flow generates a dynamically violent structure around the event horizon. The kinetic energy of the violent motion becomes equivalent to the thermal energy of the accreting disk. The shock heating due to violent motion produces a thermally driven wind which flows through the atmosphere above the accretion disk. A very thick disk, 4rh≤h,forms a narrow beam whose energy is largely supplied from hot region generated by shock wave. The accretion flowing through the thick disk,h≥ 2rh, cannot only form a single, laminar flow falling into the black hole, but also produces turbulent-like structure above the event horizon. The middle disk may possibly emit the X-ray radiation observed in active galactic nuclei. The thin disk may produce UV hump of Seyfert galaxy. Thick disk may produce a jet observed in radio galaxy. The thickness of the disk is determined by accretion rate, such ashκ κes/cṁf(r) κ 10rhṁf(r), at the inner region of the disk where the radiation pressure dominates over the gas pressure. Here, Ṁ is the accretion rate and ṁ is the normarized one by the critical-mass flux of the Eddington limit. κesandcare the opacity by electron scattering and the velocity of light.f(r) is a function with a value of unity far from the hole.

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Localization of binary black hole mergers with known inclination

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2072 ◽

2019 ◽

Vol 488 (3) ◽

pp. 4459-4463 ◽

Cited By ~ 7

Author(s):

K Rainer Corley ◽

Imre Bartos ◽

Leo P Singer ◽

Andrew R Williamson ◽

Zoltán Haiman ◽

...

Keyword(s):

Black Hole ◽

Binary System ◽

Active Galactic Nuclei ◽

Prior Information ◽

Galactic Nuclei ◽

Electromagnetic Emission ◽

Accretion Discs ◽

Host Galaxies ◽

Binary Black Hole

ABSTRACT The localization of stellar-mass binary black hole mergers using gravitational waves is critical in understanding the properties of the binaries’ host galaxies, observing possible electromagnetic emission from the mergers, or using them as a cosmological distance ladder. The precision of this localization can be substantially increased with prior astrophysical information about the binary system. In particular, constraining the inclination of the binary can reduce the distance uncertainty of the source. Here, we present the first realistic set of localizations for binary black hole mergers, including different prior constraints on the binaries’ inclinations. We find that prior information on the inclination can reduce the localization volume by a factor of 3. We discuss two astrophysical scenarios of interest: (i) follow-up searches for beamed electromagnetic/neutrino counterparts and (ii) mergers in the accretion discs of active galactic nuclei.

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Accelerating AGN jets to parsec scales using general relativistic MHD simulations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2626 ◽

2019 ◽

Vol 490 (2) ◽

pp. 2200-2218 ◽

Cited By ~ 16

Author(s):

K Chatterjee ◽

M Liska ◽

A Tchekhovskoy ◽

S B Markoff

Keyword(s):

Ambient Medium ◽

Galactic Nuclei ◽

Lorentz Factor ◽

Opening Angle ◽

Long Baseline ◽

General Relativistic ◽

Field Lines ◽

Magnetohydrodynamic Simulations ◽

Jet Collimation ◽

Sheath Structure

ABSTRACT Accreting black holes produce collimated outflows, or jets, that traverse many orders of magnitude in distance, accelerate to relativistic velocities, and collimate into tight opening angles. Of these, perhaps the least understood is jet collimation due to the interaction with the ambient medium. In order to investigate this interaction, we carried out axisymmetric general relativistic magnetohydrodynamic simulations of jets produced by a large accretion disc, spanning over 5 orders of magnitude in time and distance, at an unprecedented resolution. Supported by such a disc, the jet attains a parabolic shape, similar to the M87 galaxy jet, and the product of the Lorentz factor and the jet half-opening angle, γθ ≪ 1, similar to values found from very long baseline interferometry (VLBI) observations of active galactic nuclei (AGNs) jets; this suggests extended discs in AGNs. We find that the interaction between the jet and the ambient medium leads to the development of pinch instabilities, which produce significant radial and lateral variability across the jet by converting magnetic and kinetic energy into heat. Thus pinched regions in the jet can be detectable as radiating hotspots and may provide an ideal site for particle acceleration. Pinching also causes gas from the ambient medium to become squeezed between magnetic field lines in the jet, leading to enhanced mass loading and deceleration of the jet to non-relativistic speeds, potentially contributing to the spine-sheath structure observed in AGN outflows.

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The effects of resolution on black hole accretion simulations of jets

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2423 ◽

2020 ◽

Vol 498 (2) ◽

pp. 2428-2439

Author(s):

Christopher J White ◽

Fiona Chrystal

Keyword(s):

Black Hole ◽

Velocity Structure ◽

Grid Resolution ◽

Black Hole Accretion ◽

General Relativistic ◽

Axisymmetric Structure ◽

Magnetohydrodynamic Simulations ◽

Jet Power ◽

Hole Accretion

ABSTRACT We perform three general-relativistic magnetohydrodynamic simulations of black hole accretion designed to test how sensitive results are to grid resolution in the jet region. The cases differ only in numerics, modelling the same physical scenario of a radiatively inefficient, geometrically thick, magnetically arrested flow on to a rapidly spinning black hole. Properties inferred with the coarsest grid generally agree with those found with higher resolutions, including total jet power and its decomposition into different forms, velocity structure, non-axisymmetric structure, and the appearance of resolved millimetre images. Some measures of variability and magnetization are sensitive to resolution. We conclude that most results obtained by limiting resolution near the jet for computational expediency should still be reliable, at least in so far as they would not be improved with a finer grid.

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General Relativistic Simulation of Jet Formation from Magnetized Accretion Disk

International Astronomical Union Colloquium ◽

10.1017/s0252921100043360 ◽

1997 ◽

Vol 163 ◽

pp. 667-671

Author(s):

Shinji Koide ◽

Kazunari Shibata ◽

Takahiro Kudoh

Keyword(s):

Black Hole ◽

Active Galactic Nuclei ◽

Accretion Disk ◽

Galactic Nuclei ◽

Lorentz Factor ◽

Numerical Code ◽

Jet Formation ◽

Relativistic Jet ◽

Relativistic Regime ◽

General Relativistic

AbstractRecently, superluminal motions are observed not only from active galactic nuclei but also in our Galaxy. These phenomena are explained as relativistic jets propagating almost toward us with Lorentz factor more than 2. For the formation of such a relativistic jet, magnetically driven mechanism around a black hole is most promising. We have extended the 2.5D Newtonian MHD jet model (Shibata & Uchida 1986) to general relativistic regime. For this purpose, we have developed a general relativistic magnetohydrodynamic (GRMHD) numerical code and applied it to the simulation of the magnetized accretion disk around a black hole. We have found the formation of magnetically driven jets with 86 percent of light velocity (i.e. Lorentz factor ~ 2.0).

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