scholarly journals The Structure of Accretion Flow at the Base of Jets in AGN

2002 ◽  
Vol 19 (1) ◽  
pp. 125-128 ◽  
Author(s):  
Alina-C. Donea ◽  
Peter L. Biermann
Keyword(s):  
Boundary Layer ◽  
Black Hole ◽  
Angular Momentum ◽  
Low Power ◽  
Accretion Disk ◽  
Gravitational Energy ◽  
Kerr Geometry ◽  
Narrow Region ◽  
Stable Circular Orbit ◽  
Total Luminosity

AbstractThis paper discusses the boundary layer and the emission spectrum from an accretion disk having a jet anchored at its inner radius, close to the black hole. We summarise our earlier work and apply it to the accretion disks of some blazars. We suggest that the ‘accretion disk with jet’ (ADJ) model could make the bridge between standard accretion disk models (suitable for quasars and FRii sources) and low-power advection dominated accretion disk models (suitable for some of the low-power BL Lacs and FRi sources).The jet is collimated within a very narrow region close to the black hole (nozzle). In our model it is assumed that the boundary layer of the disk is the region between radius Rms — the last marginally stable circular orbit calculated for a Kerr geometry — and the radius Rjet, which gives the thickness of the ‘footring’, i.e. the base of the jet. We analyse the size of the boundary layer of the disk where the jet is fed with energy, mass, and angular momentum. As a consequence of the angular momentum extraction, the accretion disk beyond Rjet no longer has a Keplerian flow. A hot corona usually surrounds the disk, and entrainment of the corona along the flow could also be important for the energy and mass budget of the jet.We assume that the gravitational energy available at the footring of the jet goes into the jet, and so the spectrum from the accretion disk gives a total luminosity smaller than that of a ‘standard’ accretion disk, and our ADJ model should apply for blazars with low central luminosities. Variations of the boundary layer and nozzle may account for some of the variability observed in active galactic nuclei.

scholarly journals Launching proton-dominated jets from accreting Kerr Black Holes: the case of M87

2011 ◽  
Vol 1 (1) ◽  
pp. 4 ◽  
Author(s):  
Felix F. Brezinski ◽  
Ahmad A. Hujeirat
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Black Holes ◽  
Angular Momentum ◽  
Event Horizon ◽  
Accretion Disk ◽  
Lorentz Factor ◽  
Spin Parameter ◽  
Low Mass ◽  
Kerr Black Holes

A general relativistic model for the formation and acceleration of low mass-loaded jets from systems containing accreting black holes is presented. The model is based on previous numerical results and theoretical studies in the Newtonian regime, but modified to include the effects of space-time curvature in the vicinity of the event horizon of a spinning black hole. It is argued that the boundary layer between the Keplerian accretion disk and the event horizon is best suited for the formation and acceleration of the accretion-powered jets in active galactic nuclei and micro-quasars. The model presented here is based on matching the solutions of three different regions: i- a weakly magnetized Keplerian accretion disk in the outer part, where the transport of angular momentum is mediated through the magentorotational instability, ii- a strongly magnetized, advection-dominated and turbulent-free boundary layer (BL) between the outer cold accretion disk and the event horizon and where the plasma rotates sub-Keplerian and iii- a transition zone (TZ) between the BL and the overlying corona, where the electrons and protons are thermally uncoupled, highly dissipative and rotate super-Keplerian. In the BL, the gravitation-driven dynamical collapse of the plasma increases the strength of the poloidal magnetic field (PMF) significantly, subsequently suppressing the generation and dissipation of turbulence and turning off the primary source of heating. In this case, the BL appears much fainter than standard disk models so as if the disk truncates at a certain radius. The action of the PMF in the BL is to initiate torsional Alf`ven waves that transport angular momentum from the embedded plasma vertically into the TZ, where a significant fraction of the shear-generated toroidal magnetic field reconnects, thereby heating the protons up to the virial-temperature. Also, the strong PMF forces the electrons to cool rapidly, giving rise therefore to the formation of a gravitationally unbound two-temperature proton-dominated outflow. Our model predicts the known correlation between the Lorentz-factor and the spin parameter of the BH. It also shows that the effective surface of the BL, through which the baryons flow into the TZ, shrinks with increasing the spin parameter, implying therefore that low mass-loaded jets most likely originate from around Kerr black holes. When applying our model to the jet in the elliptical galaxy M87, we find a spin parameter <em>a ∈</em> [0.99, 0.998], a transition radius rtr ≈ 30 gravitational radii and a fraction of 0.05 − 0.1 of the mass accretion rate goes into the TZ, where the plasma speeds up its outward-oriented motion to reach a Lorentz factor Γ <em>∈</em> [2.5, 5.0] at rtr.

scholarly journals Parameter Space of Shock Formation in Adiabatic Flows

1997 ◽  
Vol 159 ◽  
pp. 72-73
Author(s):  
Ju-Fu Lu ◽  
K.N. Yu ◽  
F. Yuan ◽  
E. C. M. Young
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Parameter Space ◽  
World Line ◽  
Rest Mass ◽  
Specific Enthalpy ◽  
Shock Formation ◽  
Characteristic Functional ◽  
Kerr Geometry ◽  
Sonic Point

We study shock formation in a stationary, axisymmetric, adiabatic flow of a perfect fluid in the equatorial plane of a Kerr geometry. For such a flow, there exist two intrinsic constants of motion along a fluid world line, namely the specific total energy, E = −hut, and the specific angular momentum, l = −uφ/ut, where the uμ’s are the four velocity components, h is the specific enthalpy, i.e., h = (P + ε)/ρ, with P, ε, and ρ being the pressure, the mass-energy density, and the rest-mass density, respectively.As shown in Fig. 1 (Fig. la is for a Schwarzschild black hole, i.e. the hole’s specific angular momentum a = 0; Fig. lb is for a rapid Kerr hole, i.e. a = 0.99M, where M is the black-hole mass, and prograde flows: and Fig. 1c is for a = 0.99M and retrograde flows), in the parameter space spanned by E and l there is a strictly defined region bounded by four lines: three characteristic functional curves lk(E), lmax(E), and lmin(E), and the vertical line E = 1. Only such a flow with parameters located within this region can have two physically realizable sonic points, the inner one rin, and the outer one rout. In between there is still one more, but unrealizable, sonic point, rmid. The region is divided by another characteristic functional curve lc(E) into two parts: in region I (= Ia + Ib) only τout is realized in a shock-free global solution (i.e., that joining the black-hole horizon to large distances), while in region II (= IIa + IIb) only rin is realized.

Ratio of kinetic-to-bolometric luminosity at the “cold” disk accretion onto black holes

2018 ◽  
Vol 14 (S342) ◽  
pp. 205-208
Author(s):  
Sergey Bogovalov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Kinetic Energy ◽  
Galactic Nuclei ◽  
Gravitational Energy ◽  
Disk Accretion ◽  
Massive Black Hole ◽  
Bolometric Luminosity ◽  
Almost All

AbstractIn galactic nuclei (AGN), the kinetic energy flux of the jet may exceed the bolometric luminosity of the disk a few orders of magnitude. At the “cold” accretion the radiation from the disk is suppressed because the wind from the disk carries out almost all the angular momentum and the gravitational energy of the accreted material. We calculate an unavoidable radiation from such a disk and the ratio of the kinetic-to-bolometric luminosity from a super massive black hole in framework of the paradigm of the optically thick α-disk of Shakura & Sunyaev. The results confirm that the gravitational energy of the accreted material can be the only source of energy in AGNs.

PHYSICAL PROPERTIES OF THE THIN ACCRETION DISK OF THE TAUB-NUT BLACK HOLE

2021 ◽  
Vol 0 (1) ◽  
pp. 87-91
Author(s):  
R.M. YUSUPOVA ◽  
◽  
R.N. ZMAILOV ◽  
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Gravitational Field ◽  
Physical Properties ◽  
Accretion Disk ◽  
Energy Flow ◽  
Field Equations ◽  
Effective Potential Energy ◽  
Gravitational Field Equations ◽  
Vacuum Solutions

The Taub-NUT space-time metric is one of the vacuum solutions to Einstein's gravitational field equations. In this metric, the Newman-Unti-Tamburino parameter (NUT) and its effect on the physical properties of a thin accretion disk are of particular interest. In this paper, calculations are performed to determine the physical properties of a thin accretion disk around the Taub-NUT black hole based on the Page-Thorne model. The influence of the NUT parameter on the angular velocity, binding energy, angular momentum of particles, effective potential, energy flow, and temperature of the accretion disk is revealed. According to the data obtained, the temperature of the accretion disk of the Taub-NUT black hole decreases as the value of the NUT parameter increases.

scholarly journals An accretion disk laboratory in the Seyfert 1.9 galaxy NGC 2992

2006 ◽  
Vol 2 (S238) ◽  
pp. 123-126
Author(s):  
Tahir Yaqoob ◽  
Kendrah D. Murphy ◽  
Yuichi Terashima
Keyword(s):  
Black Hole ◽  
Emission Line ◽  
Accretion Disk ◽  
Large Amplitude ◽  
Gravitational Energy ◽  
Test Bed ◽  
Central Black Hole ◽  
X Ray ◽  
Order Of Magnitude ◽  
The Continuum

AbstractOver twenty five years of X-ray observations of the Seyfert 1.9 galaxy NGC 2992 show that it is a promising test-bed for severely constraining accretion disk models. The previous interpretation of the historical activity of NGC 2992 in terms of the accretion disk slowly becoming dormant over many years and then ‘re-building’ itself is not supported by new data. A recent year-long monitoring campaign with RXTE showed that the X-ray continuum varied by more than an order of magnitude on a timescale of weeks. During the large-amplitude flares the centroid energy of the Fe K emission-line complex became significantly redshifted, indicating that the violent activity was occurring close to the putative central black hole where gravitational energy shifts can be sufficiently large. For the continuum, the Compton-y parameter remains roughly constant despite the large-amplitude luminosity variability, with (kT) τ ∼ 20–50.

An accretion disk without angular momentum near a black hole

2012 ◽  
Vol 56 (1) ◽  
pp. 1-8
Author(s):  
V. S. Beskin ◽  
A. A. Zheltoukhov ◽  
V. I. Pariev
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disk

scholarly journals Launching proton-dominated jets from accreting Kerr Black Holes: the case of M87

2011 ◽  
Vol 1 (1) ◽  
pp. e4
Author(s):  
Felix F. Brezinski ◽  
Ahmad A. Hujeirat
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Black Holes ◽  
Angular Momentum ◽  
Event Horizon ◽  
Accretion Disk ◽  
Lorentz Factor ◽  
Spin Parameter ◽  
Low Mass ◽  
Kerr Black Holes

A general relativistic model for the formation and acceleration of low mass-loaded jets from systems containing accreting black holes is presented. The model is based on previous numerical results and theoretical studies in the Newtonian regime, but modified to include the effects of space-time curvature in the vicinity of the event horizon of a spinning black hole. It is argued that the boundary layer between the Keplerian accretion disk and the event horizon is best suited for the formation and acceleration of the accretion-powered jets in active galactic nuclei and micro-quasars. The model presented here is based on matching the solutions of three different regions: i- a weakly magnetized Keplerian accretion disk in the outer part, where the transport of angular momentum is mediated through the magentorotational instability, ii- a strongly magnetized, advection-dominated and turbulent-free boundary layer (BL) between the outer cold accretion disk and the event horizon and where the plasma rotates sub-Keplerian and iii- a transition zone (TZ) between the BL and the overlying corona, where the electrons and protons are thermally uncoupled, highly dissipative and rotate super-Keplerian. In the BL, the gravitation-driven dynamical collapse of the plasma increases the strength of the poloidal magnetic field (PMF) significantly, subsequently suppressing the generation and dissipation of turbulence and turning off the primary source of heating. In this case, the BL appears much fainter than standard disk models so as if the disk truncates at a certain radius. The action of the PMF in the BL is to initiate torsional Alf`ven waves that transport angular momentum from the embedded plasma vertically into the TZ, where a significant fraction of the shear-generated toroidal magnetic field reconnects, thereby heating the protons up to the virial-temperature. Also, the strong PMF forces the electrons to cool rapidly, giving rise therefore to the formation of a gravitationally unbound two-temperature proton-dominated outflow. Our model predicts the known correlation between the Lorentz-factor and the spin parameter of the BH. It also shows that the effective surface of the BL, through which the baryons flow into the TZ, shrinks with increasing the spin parameter, implying therefore that low mass-loaded jets most likely originate from around Kerr black holes. When applying our model to the jet in the elliptical galaxy M87, we find a spin parameter a ∈ [0.99, 0.998], a transition radius rtr ≈ 30 gravitational radii and a fraction of 0.05 − 0.1 of the mass accretion rate goes into the TZ, where the plasma speeds up its outward-oriented motion to reach a Lorentz factor Γ ∈ [2.5, 5.0] at rtr.

scholarly journals The Bardeen-Petterson effect as the precession mechanism for the radio galaxy 3C 84 (NGC 1275)

2010 ◽  
Vol 6 (S275) ◽  
pp. 182-183
Author(s):  
D. M. Teixeira ◽  
Z. Abraham ◽  
A. Caproni ◽  
D. Falceta-Gonçalves
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disk ◽  
Power Law ◽  
Surface Density ◽  
Radio Galaxy ◽  
Numerical Results ◽  
Momentum Ratio ◽  
Ngc 1275

AbstractIn this work we propose the Bardeen-Petterson effect as the precession mechanism of the jet precession in NGC 1275. To check if this is true we have estimated the angular momentum ratio and the aligment timescale predict by the theory and compared with the numerical results presented in the literature. We were able to explain the precession period assuming an accretion disk with column surface density in the form of a power law with exponent 0.6 < s < 0.7 and a black hole rotation with a spin of 0.23 < a∗<0.4.

scholarly journals Black hole accretion discs and luminous transients in failed supernovae from non-rotating supergiants

2019 ◽  
Vol 485 (1) ◽  
pp. L83-L88 ◽  
Author(s):  
E Quataert ◽  
D Lecoanet ◽  
E R Coughlin
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Accretion Discs ◽  
Necessary Condition ◽  
Mean Flow ◽  
Thermal Transients ◽  
Stable Circular Orbit ◽  
Horizontal Flows ◽  
Red Supergiants ◽  
Accretion Shock

ABSTRACT We show that for supergiants, net angular momentum is not a necessary condition for forming accretion discs during core collapse. Even absent net rotation, convective motions in the outer parts of supergiants generate mean horizontal flows at a given radius with velocities of ${\sim } 1 \, {\rm km \, s}^{-1}$; the direction of the mean flow will vary as a function of height through the convection zone. We confirm these analytic estimates using Cartesian Boussinesq convection simulations. These mean horizontal flows lead to a random angular momentum in supergiant convection zones that exceeds that of the last stable circular orbit of a black hole by a factor of ∼10. As a result, failed explosions of supergiants – in which the accretion shock on to the neutron star does not revive, leading to black hole formation – may often produce accretion discs that can power day–week (blue supergiants) or week–year (yellow and red supergiants) non-thermal and thermal transients through winds and jets. These transients will be especially time variable because the angular momentum of the accreting material will vary substantially in time. Observed sources such as Swift J1644+57, iPTF14hls, and SN 2018cow, as well as energetic Type II supernovae (OGLE-2014-SN-073), may be produced by this mechanism.

Sign in / Sign up

Export Citation Format

Share Document