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Questions tagged [accretion-disk]

An accretion disk is the disk around a compact star that accumulates matter from e.g. a companion star by the Roche lobe overflow or stellar wind transfer.

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How can a gas be in circular orbit when centrifugal force is dominant in an accretion disk around a black hole?

In the textbook "Black Holes, White Dwarfs and Neutron Stars: The Physics of Compact Objects" by Shapiro and Teukolsky, the author makes the following statement while discussing the standard thin disk ...
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Gas speed near a black hole? [duplicate]

In the book, "Black-Hole Accretion Disks: Toward a new paradigm" it is written that, "In black hole accretion, gas finally falls to the central object at the speed of light". Isn't this in ...
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Disk-like structures spectra vs ring spectra?

In the introduction to this paper (https://arxiv.org/abs/1803.06423) it is mentioned that disk-like spectra was observed in black hole X-ray binaries, when models would expected to be unstable (...
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Adiabatic and isothermal astrophysical flows

Astrophysical flows around black holes (like accretion and winds) can be adiabatic as well as isothermal. In adiabatic flows, the flow is non-dissipative except at the shock location. However, in case ...
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What causes the heating of a black hole's accretion disk?

Sheperd Doeleman said in a TED video that the accretion disk is heated by friction. Is that correct? I thought it might be adiabatic heating from the compression of the gasses.
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Can Compton scattering increase a photon's energy?

I've read (in Hagai Netzer's book The Physics and Evolution of Active Galactic Nuclei) that "Comptonization in the [black hole's accretion] disk atmosphere can increase the energy of some photons..." [...
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Vertical equilibrium condition in thin adiabatic black hole accretion flows

In adiabatic thin accretion accretion flows around black holes, we consider the vertical equilibrium condition where the thickness of the flow is very small as compared to the radial coordinate, i.e., ...
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Understanding the notion of lose or win of angular momentum in accretion disk

Here is below a slide of one of my lecture in planetology : I understand well the fact that ring A will be slow down by friction with ring B since ring B is rotating slower and the inverse process (...
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Wind-fed Accretion and White Dwarf stars

Can a White Dwarf star in a binary system accrete matter via the Wind-fed accretion process?
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Does infalling material leaves a detectable imprint on the black hole's event horizon?

An external observer will never see anything cross the event horizon, and in most explanations the story ends here. But I wonder what happens with gravitational effects of the material? For example ...
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Putting the importance of the blackhole image into perspective [closed]

The recent astonishing achievement of obtaining an actual image of a blackhole, resulted from a massive collaborative work using 8 different telescopes and the equally on par efforts in developing the ...
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Newtonian Limit of the Accretion Efficiency of a Black Hole

Netzer's book "The Physics and Evolution of Active Galactic Nuclei" (Cambridge) gives, in Section 3.2, the efficiency of a Black Hole (BH) in converting rest mass to electromagnetic radiation as: \...
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Why isn't the circumferential light around the M87 black hole's event horizon symmetric?

After the revelation of the first black hole images, it seems there is a bias towards the south side. Is it because of measuring it from earth or is it something more fundamental in the understanding ...
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How can write physics in terms of local rest fram?

Many times I saw that people wrote that we write the equations in terms of local rest frame, for example in the paper of Novikov and Thorne that calculated stress-energy tensor for Kerr blackhole ...
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How to calculate the corotation radius?

I am studying this paper: P.Ghosh & F.K.Lamb, APJ, 232, pag.259 (1979) I do not understand how the authors calculate the corotation radius, $r_{co}$, where the matter of the disk has the same ...
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If you fell into a black whole with an accretion disc, but perpendicular

If you fell into a black whole with an accretion disc, but orthogonal to the plane of the disc - would you ever meet the disc? I'm not asking whether you survive long enough, and obviously we assume ...
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How can a galaxy not be disk shaped [closed]

If a galaxy is the accretion disk for a supermassive black hole, how can it be a shape other than disk?
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Neutron Star LMXB Accretion Spin-Up Estimation

I've been asked to estimate how much mass a neutron star in a low mass X-ray binary would have to accrete in order to be spun up to ~300 Hz. I found the conservation formula $\frac{d(I\omega)}{dt} = \...
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Why does the accretion disc radiate energy and matter?

Jets of matter and energy are powered by accretion disc i.e., matter spiralling into the massive black hole at the galactic centre. How is this jet formed? I think that the dust particles and gases ...
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Is the average temperature of a big accretion disk colder than a small one?

Suppose we have a Shakura and Sunyaev style accretion disk between $r_1$ and $r_2$. What is the average temperature? We can calculate it by integrating the local temperature $$T(r)=\left [ \frac{3GM\...
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What is episodic accretion in star formation?

When I think about "episodic accretion", I imagine material from an envelope accreting only sometimes. Is that the right meaning of episodic accretion? or does it mean that the accretion rate is ...
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Resources in magnetized accretion disk

I'm looking for some resources in magnetized accretion disk. Preferably a book or an article review that starts with un-magnetized accretion disk theory. While I have some familiarity with accretion ...
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What is the density profile of Sagittarius A*'s accretion disk?

It is thought that Sagittarius A*, the supermassive black hole at the center of the Milky Way, is surrounded by an accretion disk. Can anyone provide a resource for the general density profile of ...
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Need advice on thin accretion disk model

I'm a physics teacher and I'm building a simple accretion disk model to show to students in an astrophysics class (undergraduate level), as an exemple of physics modeling. I need to know if this ...
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Paradox from mass transfer in a close stellar binary

I'm considering a simple binary system made of two stars, of mass $m_1$ and $m_2 < m_1$, on circular orbits around their center of mass. Using Newton's theory of gravitation, it is easy to prove ...
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Why can't friction in an accretion disk radiate away enough of the angular momentum do create inward spiral?

As almost every source that I'd found explains, it was a challenge for scientists to understand the mechanism by which the total angular momentum in the accretion disc was conserved, while taking the ...
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Accretion neutron star; mass gain 0.8m?

My textbook on Astrophysics says the following about accretion (translation): Assume we have a particle with mass $m$ that falls on a neutron star; $R\approx 10$ km, $M\approx 1.4M_{\text{sun}}$, ...
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overstability vs resonance: what is the difference?

Reading about discs, I encountered the word 'overstability' that its difference with resonance is not clear to me. Does anyone know the difference?
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What is the jet luminosity of this quasar (ULAS J1120+0641)?

In wikipedia I found that its luminosity is $6.3×10^{13}$ solar luminosities, but is that the luminosity of the jet itself or is that the luminosity of the entire system (the jet + the accretion disk) ...
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The difference between sub-Eddington and super-Eddington accretion disk models

I am studying accretion disks around active galactic nuclei (AGN). I have seen two sets of models, sub-Eddington and super-Eddington accretion disks. What do these terms refer to in this case? I ...
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Viscous accretion disk, green formula

I have this problem. I am studying a the viscous accretion disk problem and in the assumption of constant viscosity the equation of diffusion of the superficial density becomes: $$ \frac{\partial}{\...
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Why does most galaxies resemble a 2 dimensional plane? [duplicate]

Older galaxies mostly tend the revolve forming a disk. Why are the stars not revolving around the center of the galaxy like a sphere instead similar to electron in an atom?
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Luminosity of an accretion disk?

With reference to Black holes in particular, how can you approximate the luminosity of an accretion disk? It is possible to quantify the temperature at a given point, but as the disk is not a black ...
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Direction of Gamma Ray Bursts

After a black hole consumes a star, why do gamma ray bursts only shoot out perpendicular to the spinning accretion disk? Why do they not shoot out parallel to the disk?
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Black hole accretion disks and quasars

Are 'accretion disk of a black hole' and 'quasar' synonymous? If not, what's the difference?
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Black hole corona and bipolar outflows

What are black hole coronas? Are they different from accretion disks? If so, how are they formed?
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Black hole accretion disk

Does matter in a black hole's accretion disk eventually fall into the black hole? If no new matter is added to disk, how long does it take or the black hole to consume the entire accretion disk?
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Dependence of the magneto-rotational instability (MRI) on thermal relaxation?

The MRI is the most efficient driver of turbulence in accretion discs (as measured by the effective scalar stress). The magnetic field, being properly coupled to the gas (weak coupling), connects the ...
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Why does a black hole grow when it consumes matter? Isn't this a contradiction?

I've been thinking about this for a while but can't get my head around it. A black hole's mass is such that its gravity can overcome light. Its event horizon, as I see it, is the boundary up to which ...
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How do black hole jets form? [duplicate]

A black hole, neutron star or any object that has accumulated an accretion disc, sometimes features opposing jets, positioned perpendicular to the accretion disc. I understand that these jets are ...
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Star vs Blackhole - Accretion Disk

Simple question: can we prove that what we call today a "star" is not a accretion disk of a "tiny" black hole that happens to rotate in all the 3 axis?
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Accretion disks on neutron star binaries

Why does hydrogen gas from accretion disks not constantly get sucked onto/into a neutron star or into a black hole? I understand that some gets sucked into the black hole and some may come down and ...
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Angular momentum in planetary disk formation

This question is actually more linked to astronomy and astrophysics than to pure physics. I tried posting it on the astronomy page, however it got no answers, so I though this page might help. ...
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Would a supermassive black hole accretion disk really vaporize solid objects?

Both the movie Interstellar and Greg Egan's Incandescence involve worlds deep inside accretion disks of large holes, kept at a comfortable temperature. Is this (remotely) realistic? Although ...
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Angular momentum in an accretion disk

I need to plot the time evolution of the total angular momentum in an accretion disc. This confuses me because I thought this should be constant, since angular momentum has to be conserved? I'm given ...
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How long does it take a black hole to eat a star?

I presume the answer is that it depends on the mass and size of the star and black hole and how they approach either other, but I was wondering if somebody could provide some rough bounds (e.g. hours ...