# Gamma ray bursters

1. Aug 2, 2004

### kurious

What causes the short-lived, highly energetic, flash of light emitted by some
black holes as they are created?

2. Aug 2, 2004

### Nereid

Staff Emeritus
Could you clarify for me a bit please kurious?

Your thread title is 'gamma ray bursters', but your post refers to the creation of some black holes; clearly you have some idea that the two are somehow related - how?

Re GRBs: there are two types, 'long' and 'short'. There is some evidence to suggest that at least some of the 'long' GRBs are a kind of supernova, sometimes also called a hypernova. If so, then the observed gamma burst is a tight pair of jets which punch out of the poles of a star that's just gone hypernova. The models need a lot more work, and the observers need to provide lots more data, before one can have much confidence in these models. However, the core of the star does collapse to form a BH, but the intense jets are not directly associated with the BH, they're related to the accretion disk that forms around the collapsing core?

The 'short' GRBs continue to be an enigma; my personal favourite explanation is a starquake on a magnetar. Trouble is, there's so little data, and few models can be ruled out at present.

3. Aug 2, 2004

### kurious

Nereid:

Could you clarify for me a bit please kurious?
Your thread title is 'gamma ray bursters', but your post refers to the creation of some black holes; clearly you have some idea that the two are somehow related - how?

Kurious:
http://www.sciencedaily.com/releases/2004/07/040730091728.htm

4. Aug 2, 2004

### Entropy

Its a hypernova (massive star collapsing directly into a black hole) with its jets pointed right at us.

5. Aug 2, 2004

### Chronos

And short burst gamma sources still defy explanation. Nereid poses a valid question.

6. Aug 3, 2004

### kurious

Here's some information from WIKIPEDIA:
The brightness of GRBs varies rapidly, implying that their source objects are quite small: whatever causes the brightness variation cannot travel faster than the speed of light across the object. Very densely packed photons prevent each other from escaping, and astronomers therefore theorize that the energy initially leaves the object as a jet of matter, with gamma rays being created at a certain distance by internal shock waves.

There is some direct evidence of an association of a GRB with a supernova. A supernova synthesizes a wide range of heavy elements during its collapse, and many of these, particularly isotopes of nickel, are highly unstable and break down very quickly, releasing radiation. This means that a supernova actually gets brighter for a few days or weeks after its occurrence.

Kurious:
How do very densely packed photons prevent each other from escaping?

7. Aug 3, 2004

### Antonio Lao

The principle of superposition.

If $F_i$ is a vector for i=1,2,3,...,n and if all these vector have the same magnitude then

$$\Sigma_{i=1}^{n} F_i = nF_i$$

Implies all these vectors are collinear.

Last edited: Aug 3, 2004
8. Aug 3, 2004

### Chronos

A photon created in the core of the sun takes 10,000 years to reach the surface.

9. Aug 3, 2004

### kurious

Could gamma ray bursters be coherent photon producers like lasers - hence their great energy output? This would imply that the source star has some sort of
cavity in it for resonance perhaps? Or cavities if there are lots of wavelengths emitted.

10. Aug 3, 2004

### Nereid

Staff Emeritus
Judging by what has been observed so far, no. IIRC, some polarisation has been observed - in both optical and gamma regimes? - in one or two long GRBs, but no coherent photons. Of course, once a lot more GRBs have been carefully observed ...

11. Aug 3, 2004

### Nereid

Staff Emeritus
I'm not sure what this has to do with GRBs sol2, perhaps you can elaborate please?

AFAIK, all models of GRBs involve massive, hot, dense bodies, such as the collapsing core of a massive star (>8 sol), or a neutron star (magnetar variety); surely no place for any self-respecting BEC to hang out! Nary an atom or molecule in sight. :tongue2:

12. Aug 4, 2004

### Chronos

It is risky to extrapolate conclusions from theories you do not entirely understand. Been there, done that.

13. Aug 4, 2004

### Nereid

Staff Emeritus
I'm still at a loss sol2 - first you talk about BECs, then make a cryptic reference to magnetic fields and GPB, and link to a post about x-rays from the Milky Way centre, which itself has links to a strange site on M Theory.

What does any of this have to do with GRBs?

14. Aug 4, 2004

### sol2

From theories you do not understand? When's the last time you have joined comological events to quantum mechanics and tried to develope the relationship to quantum geometry?

If you unit electromagnetism with gravity, what would you get? What would 4d of space look like?

From that perspective, the early event would have revealled information, one in the scattering as Glast shows us and another in regards to the strength of the gravitons?

Graviton shroud?

I guess that's it.

Thanks

Last edited: Aug 4, 2004
15. Aug 4, 2004

### Nereid

Staff Emeritus
You seem to be saying that observational footprints of quantum gravity may be seen in GRBs, but so far it's all hand-waving (of just about the worst kind - vague allusions and mashed up experiments/theories/speculation) ... please show that there's some OOM reason to think that!

16. Aug 4, 2004

### sol2

What the heck do you think we are doing with Glast? High energy considerations are necessary in settling a deeper perception of reality. LQG has recognized a limit.

But until then, the leading perspectives have not changed. Some are afraid to look over the Grand Canyon because it is so vast they hold tightly to the rails:)

17. Aug 4, 2004