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trinitree88
2009-Nov-04, 12:13 AM
Gamma Ray Bursts, amongst the most energetic things we can observe and contemplate, continue to confuse and elude strict classifications. This hinders our understanding of some of the distant universe. Longs look like shorts and vice versa. Pieces of spectral data seem missing when theory seems to require that it be there. The author, Maxim Lyutikov, summarizes the state of affairs in a conference paper....at "The Shocking Universe" conference. see:http://www.merate.mi.astro.it/docM/OAB/Research/SWIFT/sanservolo2009/index.html

see:http://arxiv.org/PS_cache/arxiv/pdf/0911/0911.0349v1.pdf

RussT
2009-Nov-04, 01:29 AM
Gamma Ray Bursts, amonst the most energetic things we can observe and contemplate, continue to confuse and elude strict classifications. This hinders our understanding of some of the distant universe. Longs look like shorts and vice versa. Pieces of spectral data seem missing when theory seems to require that it be there. The author, Maxim Lyutikov, summarizes the state of affairs in a conference paper....at "The Shocking Universe" conference. see:http://www.merate.mi.astro.it/docM/OAB/Research/SWIFT/sanservolo2009/index.html

see:http://arxiv.org/PS_cache/arxiv/pdf/0911/0911.0349v1.pdf


:lol::whistle::hand::doh::wall::wall:

Don Alexander
2009-Nov-04, 05:48 PM
Now, I have not read it yet, just looked over it, but...

No, your* theory of Galactic neutron stars being impacted by comets is still wrong. :shifty:

Maxim is far and away not attacking the basics: GRBs are collimated explosions at cosmological distances, at least some of them are associated with the core collapse of massive stars, and some with galaxies that exhibit no current star formation.

The problems he points out are details in the models.

* "your" being any ATMers who now think the baby has officially been tossed out with the bath water...:whistle:

Jerry
2009-Nov-05, 07:17 PM
Now, I have not read it yet, just looked over it, but...

Maxim is far and away not attacking the basics: GRBs are collimated explosions at cosmological distances, at least some of them are associated with the core collapse of massive stars, and some with galaxies that exhibit no current star formation.

The problems he points out are details in the models.



Huh? The Title of the paper is 'Going Back to the Blackboard' which is generally what you do when your rocket/theory/pet idea explodes and you have to start over; or as the author puts it:


I argue that any present day model of GRBs, especially of Short type, is grossly incomplete.

"grossly incomplete" is NOT the same as saying "we need to work out the details".


Our lack of understanding of how GRBs work is impeding the progress and applications of GRBs, e.g., to cosmology. One can only hope that GRB theory will not suffer the same destiny as theories of pulsar radio emission: though we do not understand it and basically gave up hopes, pulsars are still very useful probes of interstellar medium and General Relativity. In case of pulsar radio emission, only about one millionth part of energy is emitted as radio waves; this make the problem especially hard. In contrast, in case of GRBs we are dealing with the dominant energy release, of the order of Solar rest mass energy in a matter of seconds. It is frustrating that we have a hard time to understand even the basic elements in such energetic phenomena.

Jerry
2009-Nov-14, 03:08 PM
http://lanl.arxiv.org/abs/0911.2328v1


Gamma-ray bursts (GRBs) are the brightest events in the universe. They have been used in the last five years to study the cosmic chemical evolution, from the local universe to the first stars. The sample size is still relatively small when compared to field galaxy surveys. However, GRBs show a universe that is surprising. At z > 2, the cold interstellar medium in galaxies is chemically evolved, with a mean metallicity of about 1/10 solar. At lower redshift (z < 1), metallicities of the ionized gas are relatively low, on average 1/6 solar. Not only is there no evidence of redshift evolution in the interval 0 < z < 6.3, but also the dispersion in the ~ 30 objects is large. This suggests that the metallicity of host galaxies is not the physical quantity triggering GRB events

Redshift evolution of metal content is one of the three pillars of the BB. Quasars have already demonstrated high metal content at high redshifts. The number of gamma ray events with chemical information is small, but the first look says we don't have a handle on metal abundance.

Another trend in gamma rays to keep an eye on, is that the duration appears to increase with cosmic age - the more rescent the burst, the longer the burst. If metallicity cannot be correlated with this apparent signature of aging, what can? Or is something more fundamental amiss?

grant hutchison
2009-Nov-14, 03:36 PM
Huh? The Title of the paper is 'Going Back to the Blackboard' which is generally what you do when your rocket/theory/pet idea explodes and you have to start over ...That's "back to the drawing board". :)
Is the "back to the blackboard" title merely a problem with translation? "Back to the drawing board" implies a complete redesign; "back to the blackboard" seems to instead imply learning new stuff and doing new calculations. From the text, I find it difficult to tell which the author really means.

Grant Hutchison

Cougar
2009-Nov-14, 04:33 PM
Gamma Ray Bursts... continue to confuse and elude strict classifications.

Well, there's physics, and everything else is stamp collecting.

trinitree88
2009-Nov-14, 04:40 PM
Well, there's physics, and everything else is stamp collecting.

Cougar. :lol: Yep. pete

Cougar
2009-Nov-14, 05:41 PM
Cougar. :lol: Yep. pete

Well, the more I think of that quote, the more I think it's perhaps a bit misguiding, if not a bit elitist. Obviously, there is great value in classifying observations of supernovae and GRBs. Such, in fact, has led to the discovery of the apparent acceleration of the expansion. No small realization there! if, in fact, the current, admittedly incomplete, explanation remains fundamentally accurate as new information flows into computer storage banks at exponential rates.

Cougar
2009-Nov-14, 06:24 PM
Redshift evolution of metal content is one of the three pillars of the BB.

I'd say that's a bit of an overstatement. That pillar is based on the abundance of the elements. The base of the pillar doesn't speak to any subsequent evolution of those abundances. Of course, the dynamics of our universe generates heavier elements. The very early history of heavy element production and dispersal is rather in the workshop of science, isn't it, as opposed to the Archives of Contingent Acceptance?

What was the temperature of the CMB at the epochs we're talking about?

bebe7
2009-Nov-16, 12:16 AM
Gamma Ray Bursts, amongst the most energetic things we can observe and contemplate, continue to confuse and elude strict classifications. This hinders our understanding of some of the distant universe. Longs look like shorts and vice versa. Pieces of spectral data seem missing when theory seems to require that it be there. The author, Maxim Lyutikov, summarizes the state of affairs in a conference paper....at "The Shocking Universe" conference. see:http://www.merate.mi.astro.it/docM/OAB/Research/SWIFT/sanservolo2009/index.html

see:http://arxiv.org/PS_cache/arxiv/pdf/0911/0911.0349v1.pdf

Quite possible GCRs are derivatives of GRBs