Questions tagged [neutron-stars]

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8
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201 views

What is the Chandrasekhar-Friedman-Schutz (CFS) instability, exactly?

I am confused as to what the Chandrasekhar-Friedman-Schutz (CFS) instability is, exactly. It seems to partially refer to this paper (https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.24.611) ...
7
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1answer
239 views

Would dark matter (as a BEC) be captured by Black Holes, Neutron Stars, etc?

Suppose that dark matter is in the form of a Bose-Einstein Condensate, with a DeBroglie wavelength of ~10,000 LY. (There are some axion models of DM where the axions are in a BEC.) In this model, the ...
3
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0answers
76 views

Neutron star merger: large scale dynamics

Yesterday was announced the first detection of a neutron star merger via gravitational and electromagnetic waves. On the announcement one of the speakers is showing a simulation of the dynamics of ...
2
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2answers
88 views

What is the energy required to create a gravitational field equivalent to that a mass $m$ shows?

If the mass of a neutron star in its collapse becomes a singularity, then the resting energy of this gravitational field must be $E = mc^2$ ($m$ = star mass). Is this possibility wrong?
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0answers
52 views

On the conversion of neutron stars in deconfined quark stars

Imagine a neutron star, constituted of nucleons ($p$, $n$) and charged leptons (say $e$ and $\mu$), can decay into a deconfined quark star through some process. Given the Bodmer-Witten hypothesis, the ...
2
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0answers
56 views

Observational evidence for superfluidity in neutron stars

What is the earliest evidence for the existence of superfluidity in neutron stars? I'm about to present the subject in a seminar and I'm under the impression that at the moment there is no ...
2
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0answers
66 views

What would happen if very light particles (of large de Broglie wavelength) encountered a neutron star?

I want to consider the possibility of a very light particle being captured by a neutron star. (For the purpose of discussion, let us allow the neutron star mass (or radius) a tunable parameter, so ...
2
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0answers
104 views

How can a neutron change its quantum state?

I was doing so research on neutron stars and I bumped into this stock exchange page. Does a neutron star burn? Quote from an awnser: The Pauli exclusion principle causes the neutrons to resist ...
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0answers
39 views

Can Thorne–Żytkow object (heavenly body) exist in universe?

Can Thorne–Żytkow object (heavenly body) exist in universe? It's a new concept I came across. Are there such heavenly bodies in universe? It's a heavenly body in which a neutron star is present inside ...
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0answers
38 views

Gravitational $N$-body mergers?

Beyond binary systems and its mergers, have numerical relativity groups computed an approximation to $N$-body GW signals/waveforms or is that a hard unsolved task?
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23 views

Strange quarks in neutron stars

Recently I have read that the pressure within neutron stars can be so extreme that it can cause the deconfinement of quarks to form a kind of quark 'soup' and that these extreme conditions allow for ...
1
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0answers
38 views

Do different neutron stars have different density?

When stars go supernova, a neutron star may be left over if there isn't enough mass to create a black hole. Based on the mass present, will a neutron star have a varying density or is the radius ...
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0answers
47 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 ...
1
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1answer
105 views

How common are neutron stars?

I thought this would be a rather easy question to answer, but it doesn't seem to be addressed anywhere. I haven't even been able to find a paper, article, or page that says it's unknown how common ...
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0answers
36 views

Examples of perturbative force-free electrodynamics on top of vacuum solutions?

Imagine I have a solution $A_{(0)\mu }$ for the four-vector potential of vacuum electrodynamics. That is, the solution fulfills source-free Maxwell equations $F^{\mu\nu}_{(0)\;\;;\nu} = 0$ with $F_{(0)...
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0answers
166 views

What does the “black body” spectrum look like from a neutrom star?

In a recent discussion I learned that when neutron stars form they cool down much quicker than a black body of the same size and temperature because they can radiate neutrinos from their interior as ...
1
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1answer
36 views

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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0answers
41 views

More conditions needed for determining the moment of inertia

I am solving the moment of inertia for a neutron star using equations: $$\frac{dI}{dr}=\frac{8\pi}{3}\frac{(\epsilon + P)f(r)j(r)r^4}{(1 − 2M/r)}\tag 1$$ $$\frac{d}{dr}\bigg(r^4j(r)\frac{df}{dr}\...
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0answers
59 views

Is there a numerical calculation for black hole - neutron star merges?

I think it might be even a more frequent event as the black hole merges. It would be similar to the black hole merges in the gravitational wave spectrum, but it could have a very clear neutrino and ...
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0answers
37 views

What's the shortest “safe” distance from a neutron star merger?

Take GW170817 for example, the first neutron star collision picked up by LIGO. Given how much data we got from that event, can anyone figure out what the "blast radius" is, and how far away from the ...
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0answers
24 views

Neutron star modelling with polytrope

I want to model the density profile of a neutron star with 1.4 $M_\odot$ with a polytrope $p=\kappa\rho^{\gamma}$ with $\gamma=1+\frac{1}{n}$. I started with $n=\frac{1}{2}$ and solved the Lane-Emden ...
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45 views

How does a Thorne Zytkow star die?

A Thorne-Zytkow star is one where a red giant or supergiant contains a neutron star at its core, formed from the collision of the giant with the neutron star. It is believed that one has been found in ...
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42 views

Doubt about the Einstein Field Equations (EFE) of a Magnetar

The Schwarzschild solution could be an good model for a planet and a star, without rotation and electric and magnetic charge. Besides the fact that this solution is spherically symmetric. The metric ...
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0answers
50 views

Is there a relatively painless way to calculate the radius of a neutron star, given its mass?

I know there are different models based on, as I understand it, different equations of state describing the neutron star mass-raduis relation. I'm not sure what to do with that, though. My math isn't ...
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0answers
29 views

Is getting nudged from a neutron star to a black hole catastrophic?

A recently released SF book has single neutron star on the veritable edge of collapsing into a black hole... "What's going on with the star?" "It's massive. I mean, like, spit-on-it-and-it'll-...
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91 views

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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1answer
30 views

Phase transition and energy conservation inside neutron star

I'm stuck at the moment with this simple question: If a phase transition from hadronic to quark matter of 1st order with a big jump in the energy density occurs inside a neutron star one can get ...
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5answers
105 views

How does gravity acts on the electrons to collapse a neutrons star or white dwarfs against the degeneracy pressure?

if electrons is considered as quantum particle in case neutron star (alluding to quantum statistics) how does gravity makes the star collapse? considering the fact that electrons are quantum particles ...
0
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1answer
163 views

Qualitative picture or reference for a Lemaître's Cold Big Bang theory

Warning: please, consider this question to be motivated by historical curiosity or as an exercise in model-building. I believe this cannot be considered non-mainstream physics as it was very much ...
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1answer
117 views

what is meant by Newtonian Polytrope?

I study about newtonian polytrope n = 1 that for this polytrope steller radius does not depend on mass and central density. I want to know are there some more polytropes that are known as newtonian ...
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1answer
182 views

In TOV equations of hydrostatic equilibrium

in TOV equations of hydrostatic equilibrium $\{P(r),M(r),v(r)\}$ are coupled with 1st order and $P(r)$ , $M(r)$ have initial values at $r=0$ but $v(r)$ is at the boundary of the star. Therefore, when ...