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.

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 Dynamics of charged and rotating NUT black holes in Rastall gravity

2020 ◽  
Vol 29 (03) ◽  
pp. 2050021
Author(s):  
Hadyan L. Prihadi ◽  
Muhammad F. A. R. Sakti ◽  
Getbogi Hikmawan ◽  
Freddy P. Zen
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Thermodynamic Properties ◽  
Circular Orbit ◽  
Black Hole Solution ◽  
Event Horizons ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

In this work, the Kerr–Newman-NUT black hole solution in Rastall gravity is proposed and it turns out that the horizon is [Formula: see text] dependence. Black hole dynamics such as the event horizons, ergosurface, zero angular momentum observer (ZAMO), thermodynamic properties, and the equatorial circular orbit around the black hole such as static radius limit, null equatorial circular orbit, and innermost stable circular orbit are investigated in this work. How the NUT and Rastall parameter affect the dynamic of the black hole is also shown.

Circular motion and the innermost stable circular orbit for spinning particles around a charged Hayward black hole background

2020 ◽  
pp. 2050121
Author(s):  
Eduard Larrañaga
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Test Particle ◽  
Circular Orbit ◽  
Supplementary Condition ◽  
Spinning Particles ◽  
Black Hole Background ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

The circular orbits of a spinning test particle moving around a charged Hayward black hole is investigated by using the Mathisson–Papapetrou–Dixon equations together with the Tulczyjew spin-supplementary condition. By writing the equations of motion, the effective potential for the description of the test particle is obtained to study the properties of the Innermost Stable Circular Orbit (ISCO). The results show that the ISCO radii for spinning particles moving in the charged Hayward background differ from those obtained in the corresponding Schwarzschild or Reissner–Nordstrom spacetimes, depending on the values of the electric charge and the length-scale parameter of the metric. When the spin of the particle and its orbital angular momentum are aligned, an increase in the spin produces a decrease in the ISCO radius, while in the case in which the spin of the particle and its orbital angular momentum are anti-aligned, an increase in the spin results in an increase of the radius of the ISCO.

7. Eating more and growing bigger

2015 ◽  
Author(s):  
Katherine Blundell
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Discs

How do black holes grow? There is a lot of matter orbiting around a black hole and this matter can interact with itself, but must observe the laws of gravity and conservation of angular momentum. ‘Eating more and growing bigger’ explains that the accreting matter is very often in the form of a disc. It goes on to discuss what accretion discs look like, how hot they are, and how you measure how fast a black hole is spinning. How close matter is able to orbit before being swallowed by the black hole tells you how fast the black hole itself must be spinning.

scholarly journals Infrared effects in the late stages of black hole evaporation

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Éanna É. Flanagan
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Planck Scale ◽  
Black Hole Mass ◽  
Order Unity ◽  
Intrinsic Angular Momentum ◽  
Hole Position ◽  
Late Stages ◽  
Shear Tensor

Abstract As a black hole evaporates, each outgoing Hawking quantum carries away some of the black holes asymptotic charges associated with the extended Bondi-Metzner-Sachs group. These include the Poincaré charges of energy, linear momentum, intrinsic angular momentum, and orbital angular momentum or center-of-mass charge, as well as extensions of these quantities associated with supertranslations and super-Lorentz transformations, namely supermomentum, superspin and super center-of-mass charges (also known as soft hair). Since each emitted quantum has fluctuations that are of order unity, fluctuations in the black hole’s charges grow over the course of the evaporation. We estimate the scale of these fluctuations using a simple model. The results are, in Planck units: (i) The black hole position has a uncertainty of $$ \sim {M}_i^2 $$ ∼ M i 2 at late times, where Mi is the initial mass (previously found by Page). (ii) The black hole mass M has an uncertainty of order the mass M itself at the epoch when M ∼ $$ {M}_i^{2/3} $$ M i 2 / 3 , well before the Planck scale is reached. Correspondingly, the time at which the evaporation ends has an uncertainty of order $$ \sim {M}_i^2 $$ ∼ M i 2 . (iii) The supermomentum and superspin charges are not independent but are determined from the Poincaré charges and the super center-of-mass charges. (iv) The supertranslation that characterizes the super center-of-mass charges has fluctuations at multipole orders l of order unity that are of order unity in Planck units. At large l, there is a power law spectrum of fluctuations that extends up to l ∼ $$ {M}_i^2/M $$ M i 2 / M , beyond which the fluctuations fall off exponentially, with corresponding total rms shear tensor fluctuations ∼ MiM−3/2.

scholarly journals A full relativistic thin disc - the physics of the plunging region and the value of the stress at the ISCO

2021 ◽  
Author(s):  
William J Potter
Keyword(s):  
Black Hole ◽  
Surface Temperature ◽  
Accretion Rate ◽  
Speed Of Light ◽  
Thin Disc ◽  
Stable Circular Orbit ◽  
Stress Surface ◽  
Innermost Stable Circular Orbit ◽  
Turbulent Heating ◽  
Local Surface Temperature

Abstract The widely used Novikov-Thorne relativistic thin disc equations are only valid down to the radius of the innermost-stable circular orbit (ISCO). This leads to an undetermined boundary condition at the ISCO, known as the inner stress of the disc, which sets the luminosity of the disc at the ISCO and introduces considerable ambiguity in accurately determining the mass, spin and accretion rate of black holes from observed spectra. We resolve this ambiguity by self-consistently extending the relativistic disc solution through the ISCO to the black hole horizon by calculating the inspiral of an average disc particle subject to turbulent disc forces, using a new particle-in-disc technique. Traditionally it has been assumed that the stress at the ISCO is zero, with material plunging approximately radially into the black hole at close to the speed of light. We demonstrate that in fact the inspiral is less severe, with several (∼4 − 17) orbits completed before the horizon. This leads to a small non-zero stress and luminosity at and inside the ISCO, with a local surface temperature at the ISCO between ∼0.15 − 0.3 times the maximum surface temperature of the disc, in the case where no dynamically important net magnetic field is present. For a range of disc parameters we calculate the value of the inner stress/surface temperature, which is required when fitting relativistic thin disc models to observations. We resolve a problem in relativistic slim disc models in which turbulent heating becomes inaccurate and falls to zero inside the plunging region.

scholarly journals Gaseous Disks in the Nuclei of Elliptical Galaxies

1997 ◽  
Vol 163 ◽  
pp. 620-625 ◽  
Author(s):  
H. Ford ◽  
Z. Tsvetanov ◽  
L. Ferrarese ◽  
G. Kriss ◽  
W. Jaffe ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Elliptical Galaxies ◽  
Central Mass ◽  
Massive Black Holes ◽  
Radio Jets

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.

scholarly journals Nuclear burning in collapsar accretion discs

2020 ◽  
Vol 499 (3) ◽  
pp. 4097-4113 ◽  
Author(s):  
Yossef Zenati ◽  
Daniel M Siegel ◽  
Brian D Metzger ◽  
Hagai B Perets
Keyword(s):  
Angular Momentum ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
Reaction Network ◽  
Accretion Discs ◽  
Late Time ◽  
Rotating Stars ◽  
Stellar Envelope ◽  
Nuclear Burning ◽  
R Process

ABSTRACT The core collapse of massive, rapidly-rotating stars are thought to be the progenitors of long-duration gamma-ray bursts (GRB) and their associated hyperenergetic supernovae (SNe). At early times after the collapse, relatively low angular momentum material from the infalling stellar envelope will circularize into an accretion disc located just outside the black hole horizon, resulting in high accretion rates necessary to power a GRB jet. Temperatures in the disc mid-plane at these small radii are sufficiently high to dissociate nuclei, while outflows from the disc can be neutron-rich and may synthesize r-process nuclei. However, at later times, and for high progenitor angular momentum, the outer layers of the stellar envelope can circularize at larger radii ≳ 107 cm, where nuclear reactions can take place in the disc mid-plane (e.g. 4He + 16O → 20Ne + γ). Here we explore the effects of nuclear burning on collapsar accretion discs and their outflows by means of hydrodynamical α-viscosity torus simulations coupled to a 19-isotope nuclear reaction network, which are designed to mimic the late infall epochs in collapsar evolution when the viscous time of the torus has become comparable to the envelope fall-back time. Our results address several key questions, such as the conditions for quiescent burning and accretion versus detonation and the generation of 56Ni in disc outflows, which we show could contribute significantly to powering GRB SNe. Being located in the slowest, innermost layers of the ejecta, the latter could provide the radioactive heating source necessary to make the spectral signatures of r-process elements visible in late-time GRB-SNe spectra.

scholarly journals Circum-nuclear molecular disks: Role in AGN fueling and feedback

2019 ◽  
Vol 15 (S359) ◽  
pp. 312-317
Author(s):  
Francoise Combes
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
High Resolution ◽  
Large Scale ◽  
Active Galaxy ◽  
Small Scale ◽  
Massive Black Hole ◽  
Molecular Outflows ◽  
Molecular Outflow

AbstractGas fueling AGN (Active Galaxy Nuclei) is now traceable at high-resolution with ALMA (Atacama Large Millimeter Array) and NOEMA (NOrthern Extended Millimeter Array). Dynamical mechanisms are essential to exchange angular momentum and drive the gas to the super-massive black hole. While at 100pc scale, the gas is sometimes stalled in nuclear rings, recent observations reaching 10pc scale (50mas), may bring smoking gun evidence of fueling, within a randomly oriented nuclear gas disk. AGN feedback is also observed, in the form of narrow and collimated molecular outflows, which point towards the radio mode, or entrainment by a radio jet. Precession has been observed in a molecular outflow, indicating the precession of the radio jet. One of the best candidates for precession is the Bardeen-Petterson effect at small scale, which exerts a torque on the accreting material, and produces an extended disk warp. The misalignment between the inner and large-scale disk, enhances the coupling of the AGN feedback, since the jet sweeps a large part of the molecular disk.

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