Gamma Ray Bursts

SHISHKABOB

I've been reading about gamma ray bursts (GRBs) lately and have found them to be pretty interesting. As far as I have read, it appears that we still don't know much about what actually causes them, or rather, how the "internal engine" works.

The most popular idea for longer lasting GRBs is a very massive star, 30 solar masses I think, going supernova, right?

Is there a lot of interest in GRBs today? Is it a good field of study to look into?

phyzguy

GRBs are a very active field in astrophysics today. There appear to be two types - long GRBs (which last longer than ~ 1 second) and short GRBs (typically shorter than 1 seond). The long GRBs are pretty firmly established to be caused by supernova collapse of massive stars, as you said. In a few cases an optical supernova (of Type Ic if you're familiar with the nomenclature) has been seen that correspond to the long GRB. The best model for the short GRBs is that the represent the merger of two neutron stars, but this is much less firmly established.

Chronos

Perhaps the title is a bit over stated, but, this is the latest news on short GRB's
http://www.sciencedaily.com/releases...0407132618.htm

Dotini

..and here's some up to date research, video included, from NASA: http://www.space.com/15119-mysteriou...e-objects.html

The Fermi space telescope has spotted nearly 500 powerful gamma-ray sources in deep space over the last three years. Before its launch in 2008, scientists only knew of four such objects.

"We're not looking for the ordinary things," Thompson said. "We're looking for the extraordinary; powerful things that might produce gamma rays."

Of the newly discovered bodies, more than half are active galaxies. Pulsars and supernova remnants each make up about 5 percent of the sources, with high-mass binary stars and other galaxies contributing just a smidge more, the researchers said.

Yet a large collection of objects remains unidentified, they added.


Edit: I found this interesting story,
http://www.newscientist.com/article/...ern-skies.html


Respectfully submitted,
Steve

SHISHKABOB

Isn't there a difference between gamma ray sources and gamma ray bursts? Like I know the Fermi Bubbles are thought to perhaps be large outflows of supernova wind material reacting with the intergalactic medium (I think).

however, it is still a very interesting article. Pretty nifty that they've found so many things in the sky that are complete mysteries.

Bobbywhy

SHISHKABOB, these may help in your quest:

"New results out of Antarctica support the idea that the most energetic of the superspeedy space particles raining down on Earth are not from gamma-ray bursts. The conclusion, reported in the April 19 Nature, has upped the ante on a long-standing mystery in astrophysics."
http://www.skyandtelescope.com/news/...148267685.html

Nature | Letter
“An absence of neutrinos associated with cosmic-ray acceleration in γ-ray bursts
IceCube Collaboration”

“Very energetic astrophysical events are required to accelerate cosmic rays to above 1018 electronvolts (Etavolts). GRBs (γ-ray bursts) have been proposed as possible candidate sources. In the GRB ‘fireball’ model, cosmic-ray acceleration should be accompanied by neutrinos produced in the decay of charged pions created in interactions between the high-energy cosmic-ray protons and γ-rays. Previous searches for such neutrinos found none, but the constraints were weak because the sensitivity was at best approximately equal to the predicted flux. Here we report an upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions. This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 1018 electronvolts or that the efficiency of neutrino production is much lower than has been predicted.”
http://www.nature.com/nature/journal...ture11068.html