How Does Eddington Luminosity Limit Black Hole Mass Accretion Rates?

Thread starter fishlens
Start date Nov 13, 2019
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Accretion Mass Maximum

In summary, accretion is the process of matter accumulating onto an object through gravitational attraction. It can lead to the formation of maximum mass objects like neutron stars and black holes when the mass becomes too great for the object to support. The maximum mass an object can reach through accretion depends on factors like initial mass, accretion rate, and gravity strength. However, accretion cannot continue indefinitely and will eventually reach a maximum mass before stabilizing or collapsing. The maximum mass of an object is determined by the balance between gravity and outward forces like pressure or rotation, which can vary based on composition and environment.

Nov 13, 2019

fishlens

Homework Statement: I need help with the following problem (this is from the book Accretion Power in Astrophysics):

Consider a black hole accreting spherically symmetrically from a fixed medium (constant density and temperature). What is the maximum mass a seed black hole could
grow to before its luminosity would limit further growth? Assume that the efficiency
η for spherically symmetrical accretion is a free parameter. Calculate its value for
fiducial ISM parameters, T = 104 K, n = 1 cm−3. Does this maximum mass have
an astrophysical interpretation?

Relevant Equations: L_edd = 13*10^38 M/M_sun [erg s-1]

The Eddington luminosity gives a limit on the mass accretion rate of the black hole and therefore of the mass of the black hole.
L_edd = 13*10^38 M/M_sun [erg s-1]. When I calculate from this I get that the maximum mass is M = 10^(-8)M_sun... which is impossible. Any ideas?

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Nov 14, 2019

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How did you get that mass?
Or, asked differently, what did you use as luminosity?

1. What is accretion?

Accretion refers to the process by which matter accumulates and forms larger objects, such as planets, stars, or galaxies. This typically occurs due to the gravitational attraction between particles and their subsequent collision and merging.

2. How does accretion contribute to the maximum mass of an object?

The maximum mass of an object is determined by the balance between the force of gravity pulling matter in and the internal pressure pushing matter out. Accretion can increase an object's mass, but if the internal pressure cannot keep up, the object will eventually collapse under its own weight.

3. What is the maximum mass that an object can reach through accretion?

The maximum mass an object can reach through accretion depends on various factors, such as the object's composition, temperature, and pressure. For example, the maximum mass of a star is determined by its ability to fuse hydrogen into helium in its core.

4. Can accretion continue indefinitely?

No, accretion cannot continue indefinitely. As an object becomes more massive, its internal pressure increases, making it more difficult for additional matter to be accreted. Eventually, the object will reach a maximum mass and will not be able to accrete any more matter.

5. How does the rate of accretion affect the maximum mass of an object?

The rate of accretion can affect the maximum mass of an object in various ways. A higher rate of accretion can lead to a faster increase in mass, but it can also result in a higher internal pressure, which may limit the object's maximum mass. Additionally, if the rate of accretion is too high, it can cause the object to become unstable and potentially disrupt its growth process.