All Questions
Tagged with black-holes binary-stars
34
questions
6
votes
1
answer
92
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Extreme Mass Ratio Inspirals and GWs cycles
I was reading through the following paper GRMHD study of accreting massive black hole binaries in astrophysical environment: A review. Therein, we have the following image
It is not quite clear how ...
- 1,213
4
votes
1
answer
87
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Do we use transit photometry to look for a black hole star binary systems?
What would a light curve look like for a black hole transiting a star? Initially I thought it would bend all light essentially blacking out a star but we would probably still detect some however the ...
- 1,348
4
votes
0
answers
85
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Hills Mechanism
The Hills mechanism postulates that when a stellar binary system is perturbed by a supermassive black hole (SMBH), the tidal forces at play result in the capture of one star while simultaneously ...
- 1,213
1
vote
1
answer
46
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Closest possible orbital radius for equal masses
If you have two objects of equal mass, then what’s the closest distance that they can orbit at in terms of their schwarzschild radii? How fast would they be orbiting?
What About stable orbits?
- 2,908
1
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1
answer
47
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If two black holes orbit around each other should their tidal forces cause a shrinking of the closer parts of their event horizons?
I recently asked a question about the influence of external gravitational fields on the stability of the geometry of a part or all the event horizon of a black hole. I understood the answer in a ...
- 2,255
0
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1
answer
37
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Invariance of binary black hole gravitational waves
Why BBH gravitational waves can be parameterized with the mass ratio? (and is not necessary the value of the two masses explicitly)
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1
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66
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Does SXS catalog for NR simulations have non-spinning, non-eccentric blackholes?
I am looking for NR waveform for two non-spinning and non-eccentric black hole binary merger for small mass ratio. Somehow, on the SXS catalog website, I don't see any such description.
Thanks
- 125
2
votes
1
answer
40
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Should a black holes binary system in fase of imminent merge shrink the parts of the event horizons of both black holes where they face each other?
Should a black holes binary system in fase of imminent merge shrink the inner parts of the event horizons of both black holes where they directly face each other? So the 'singularities' have the inner ...
- 2,255
0
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1
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How to convert from polarization modes ($h_{+}$, $h_{×}$) to obtain spin-weighted spherical harmonic $h_{lm}$ as a function of $h_{+}$, $h_{×}$?
This question arises from a discussion in the thread How to convert from plus and cross polarization modes ($h_{+}$, $h_{×}$) to spin-weighted spherical harmonic $h_{lm}$?
I was looking for a ...
- 125
16
votes
3
answers
2k
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Time dilation effects at the center of a binary black hole system
Imagine two identical black holes in a circular orbit, and Alice is smack-dab in the middle of the system (at the barycenter). Bob is at infinity.
Let's assume that Alice and Bob are stationary ...
- 779
6
votes
2
answers
715
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Can two relativistic black holes' event horizons overlap and separate again?
I have read this question:
What I have not seen is a purely classical argument for the non-separation of a black hole merger. One can obviously take the time reversed spacetime manifold of a merger ...
- 29k
0
votes
1
answer
79
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Gauge independence of the gravitational-wave frequency and gauge dependence of the binary separation?
In the seminal paper by Cutler & Flanagan (1994), which uses multi-timescale analysis to derive waveforms in the post-Newtonian approximation without spin effects, they state that,
"In Eq. (...
- 2,749
5
votes
2
answers
221
views
Black holes: Is merger inevitable when horizons touch?
I watched a simulation of the binary black hole merger of 2019 April 12
https://www.ligo.caltech.edu/video/ligo20200420v1
When the "apparent horizons" (their terminology; are those ...
- 265
5
votes
1
answer
423
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Is there an approximate expression for the force between two black holes?
Just curious: is there an approximate expression for the gravitational attraction between two Schwarzschild black holes of masses $M$ and $m$, held without relative speed at some center to center ...
user85598
-2
votes
1
answer
90
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An apparent paradox in General relativity using a binary black hole
Note: Quantum gravity effects are ignored in this question.
Imagine 2 black holes each with mass $m$ approaching each other and after some time the Event Horizons (EHs) of both black holes touch each ...
- 1,580
8
votes
2
answers
959
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In which direction would gravitational waves be emitted when two black holes colide?
Imagine two black holes on the x-axis coming together at the origin (not rotating around each other, just falling towards each other).
In which direction would the most intense gravitational waves be ...
user84158
1
vote
1
answer
94
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Are there any black hole neutron star binary?
Has a black hole-neutron star binary aver been observed?
I mean observed in any way: gravitationally, through eclipse, or any other means.
EDIT Thanks to the comment to this question, we know that ...
- 1,335
4
votes
3
answers
262
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What happens to the accretion disk when two black holes merge?
I'm aware that accretion disks around black holes are formed from the swirling mass of matter that is slowly being stripped of its atoms, but what happens to it when two black holes merge? I was ...
- 87
1
vote
1
answer
188
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Event-Horizon Shape in a Binary System
I understand that a solitary black hole has a spherical event horizon.
I was wondering whether this still stands in a binary system of two (let's say equal mass) black holes? Could the proximity of ...
7
votes
1
answer
283
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Theoretical solution to binary black hole merger based on Hawking and Ellis
Following Hawking and Ellis, Chapter 9, Fig. 60, Pg. 322, the following figure is meant to illustrate the contrast between apparent horizons and event horizons in the case of a binary black hole ...
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9
votes
3
answers
2k
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How do inspiraling black holes get closer?
In Newtonian mechanics, binaries are stable. We here on earth are very glad that it will not emit its angular momentum and spiral into the sun. What is different about the black holes and neutron ...
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2
votes
2
answers
216
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Time dilation, and curvature of space caused by two black holes of unequal masses
If you were to try to find the time dilation in a region of space near a black hole you would use the equation
$$t_r=\sqrt{1-\frac{2GM}{rc^2}}$$
Would the time dilation from two black holes be this?
...
- 780
1
vote
0
answers
71
views
Magnetar's magnetic field near a black hole (novice question)
Even light cannot escape the event horizon of a black hole. Now, imagine a magnetar orbits a black hole. The magnetar orbits too far to be ripped and consumed by the black-hole. However, its magnetic ...
- 409
3
votes
1
answer
286
views
Penrose diagram for two black holes?
Is there a Penrose diagram for two black holes near each other. Perhaps they are colliding or circling each other? Or can this method only describe a single black hole.
user84158
2
votes
1
answer
553
views
What happens to the singularities of two black holes in the moment they merger?
Let's assume the merger of a binary black hole and consider especially the moment of the transition from the last stable orbit to the merger, i.e. the transition where two black holes form one black ...
- 1,589
0
votes
1
answer
300
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Binary System in General Relativity: Analytical Metric? [duplicate]
My question is quite simple, why an analytical metric can't be found for a static binary system, even for a system under the Schwarschild condition : low field, in the vacuum between the bodies so $T_{...
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2
votes
2
answers
339
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Spacetime geometry with a system of $n$ interacting black holes [closed]
The Schwarzschild metric is given by $ds^2=-\left(1-\frac{2GM}{rc^2}c^2\right)dt^2+\left(1-\frac{2GM}{rc^2}c^2\right)^{-1}dr^2+r^2d\Omega^2,$ for $d\Omega^2$ the round metric on the $2$-sphere, in ...
- 153
0
votes
0
answers
1k
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Quadrupole moment tensor
I am currently working on gravitational waves, and as in every lecture on general relativity I derived the symmetric trace-free perturbation of a Minkowski metric with the Lorenz gauge condition, ...
- 566
6
votes
2
answers
1k
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What happens to the angular momentum of two merging black holes?
Suppose that two black holes of roughly equal mass in a binary system, formed from say a large mass stellar binary system, are in orbits around their center of mass. Further, suppose that we are ...
- 545
0
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2
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247
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Can a binary star system create a stationary black hole?
Research over the last 200 years suggests that half or more of visible stars are part of multiple star systems.
I apologise for the number of assumptions in my question but, because of the numbers of ...
user108787