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Accretion disc rigidity



 
 
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  #1  
Old May 26th 11, 02:57 PM posted to sci.astro
Frisbieinstein
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Default Accretion disc rigidity

How rigid might the accretion disk of a neutron star be? Rigid
enough to vibrate?
  #2  
Old May 26th 11, 03:29 PM posted to sci.astro
[email protected]
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Default Accretion disc rigidity

On 2011-05-26, Frisbieinstein wrote:
How rigid might the accretion disk of a neutron star be? Rigid
enough to vibrate?


It's not a solid object.

Bud

  #6  
Old June 6th 11, 09:03 PM posted to sci.astro
Steve Willner
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Default Accretion disc rigidity

In article 00,
eric gisse writes:
I just noticed that I missed something obvious. Since when do neutron stars
support accretion disks?


Aren't a lot of X-ray binaries accretion disks around neutron stars?

SW Why would p-waves or gravity waves necessarily be damped out quickly?

I believe my guess at the time was that the turbulence of the medium
coupled with its' relative low density makes it hard to support waves that
could propagate for meaningful stretches.


Turbulence might be a problem, but I'm not sure low density is.
Plasmas are pretty well coupled because of the charges. (By the way,
possessive pronouns don't have apostrophes, though sometimes I put
them in by accident myself.)

SW I vaguely recall some X-ray variability evidence...

It had to do with near-periodic X-ray variability, but I don't
remember the circumstances or reference and may be mistaken about the
whole thing.

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  #7  
Old June 7th 11, 04:17 AM posted to sci.astro
eric gisse
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Default Accretion disc rigidity

(Steve Willner) wrote in
:

In article 00,
eric gisse writes:
I just noticed that I missed something obvious. Since when do neutron
stars support accretion disks?


Aren't a lot of X-ray binaries accretion disks around neutron stars?


When I hear 'accretion disk' I tend to think exclusively 'black hole'
because neutron stars aren't massive enough to generate a construct that
is many diameters larger than the object.

I know that binary systems with a neutron star and a regular star at
close orbital distances can result in matter being stripped off the star
and thrown onto the surface of the neutron star.


SW Why would p-waves or gravity waves necessarily be damped out
quickly?

I believe my guess at the time was that the turbulence of the medium
coupled with its' relative low density makes it hard to support waves
that could propagate for meaningful stretches.


Turbulence might be a problem, but I'm not sure low density is.
Plasmas are pretty well coupled because of the charges. (By the way,
possessive pronouns don't have apostrophes, though sometimes I put
them in by accident myself.)


Yeah I'm not glossing over how plasmas are coupled or how you can have
things like Alven waves.

The main thinking is that low frequency oscillations (gravity waves
aren't the fastest, iirc) can not be physically supported by the plasma
via some frequency cutoff whose name I forget. The other degree of
thinking is that high frequency oscillations will be radiated away or
straight up absorbed via turbulence, considering the nature of an
accretion disk.

Its' all very qualitative, I could be talking nonsense.
indicate posession was the proper thing to do. *shrug


SW I vaguely recall some X-ray variability evidence...

It had to do with near-periodic X-ray variability, but I don't
remember the circumstances or reference and may be mistaken about the
whole thing.


  #8  
Old June 10th 11, 09:43 PM posted to sci.astro
Steve Willner
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Posts: 1,172
Default Accretion disc rigidity

In article 00,
eric gisse writes:
I know that binary systems with a neutron star and a regular star at
close orbital distances can result in matter being stripped off the star
and thrown onto the surface of the neutron star.


Neutron star X-ray binaries are pretty common. Cygnus X-2 is one
famous example. The X-rays come from an accretion disk.

... high frequency oscillations will be radiated away or
straight up absorbed via turbulence, considering the nature of an
accretion disk.


I think the part about turbulence is right, though I'm not sure
"absorbed" is quite the right word. I don't see how waves in plasma
can be "radiated away," though, whether the restoring force is
pressure or gravity.

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Help keep our newsgroup healthy; please don't feed the trolls.
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  #9  
Old June 10th 11, 10:08 PM posted to sci.astro
Androcles[_44_]
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Posts: 67
Default Accretion disc rigidity


"Steve Willner" wrote in message
...
| In article 00,
| eric gisse writes:
| I know that binary systems with a neutron star and a regular star at
| close orbital distances can result in matter being stripped off the star
| and thrown onto the surface of the neutron star.
|
| Neutron star X-ray binaries are pretty common. Cygnus X-2 is one
| famous example. The X-rays come from an accretion disk.

Chocolate eggs are pretty common. Cadbury's Roses is one
famous example. The eggs come from the Easter Bunny.

Nunquam ponenda est pluralitas sine necessitate (Pluralities ought not be
posited without necessity)
- William of Occam, from Quaestiones et decisiones in quattuor libros
Sententiarum Petri Lombardi




 




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