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Fraser
2004-Aug-05, 05:05 PM
SUMMARY: The European Space Agency's Integral probe detected a gamma ray burst in December 2003, which has now been studied by a host of telescopes and instruments for several months. Researchers now believe that the event, called GRB 031203, was the closest burst on record; it went off in a galaxy only 1.3 billion light-years away. Even though it was much closer, it wasn't much brighter than other bursts, and astronomers believe this could be the first discovery of a whole new class of gamma ray bursts which aren't as energetic, but could be much more common.

What do you think about this story? Post your comments below.

jitte
2004-Aug-05, 05:32 PM
From the article:

"Cosmic gamma-ray bursts (GRBs) are flashes of gamma rays that can last from less than a second to a few minutes and occur at random positions in the sky. A large fraction of them is thought to result when a black hole is created from a dying star in a distant galaxy."

Since this burst was so dim, do they believe it had a source other than a supernova? I couldn't tell from the article.

om@umr.edu
2004-Aug-05, 08:58 PM
Gail McLaughlin of North Carolina State University and Stan Woosley of UC-Santa Cruz presented papers concerning gamma-ray bursts (GRBs) and supernovae (SNs) nucleosynthesis at the NIC8 conference in Vancouver a couple of weeks ago.

Here are my conclusions from their talks:

1) GRBs are not in the galactic plane, but have an isotropic distribution.

2) GRBs are associated with asymmetric explosion of Type I supernovae (SNs).

2a) GRB980425 announced the birth of SN1998bw.
2b) GRB030329 announced the birth of SN2003dh.
2c) The SN typically occurs a few days after the GRB.

3) After consideration of the 5-degree angle of the departing gamma rays, it is estimated that about 1% of SNs are preceeded by GRBs.

4) SN explosions occur at a rate of about 1 in 30-100 year, i.e. about 0.01 yr^(-1).

5) GRBs occur at a rate of about 1 in 100,000 year, i.e., about 0.00001 yr^(-1).

6) GRBs are believed to make Ni-56.

7) Neutrinos may power the jets squirting in opposite directions.

With kind regards,

Oliver
http://www.umr.edu/~om

antoniseb
2004-Aug-05, 10:54 PM
Here are a couple of more detailed papers about these lower luminosity GRBs:

An apparently normal γ-ray burst with an unusually low luminosity (http://www.arxiv.org/PS_cache/astro-ph/pdf/0408/0408095.pdf).

The sub-energetic GRB031203 as a cosmic analogue to GRB980425 (http://www.arxiv.org/PS_cache/astro-ph/pdf/0408/0408096.pdf)

Algenon the mouse
2004-Aug-06, 12:48 AM
I understand that these gamma rays also can sterilize a planet of life. Anyone else hear this?

antoniseb
2004-Aug-06, 01:58 AM
Originally posted by Algenon the mouse@Aug 6 2004, 12:48 AM
I understand that these gamma rays also can sterilize a planet of life. Anyone else hear this?
It depends on how far away the GRB is from the planet.
If the GRB is on the other side of the same galaxy, but aimed right at a planet, it will cause a mass extinction, but probably will not harm the things growing around undersea volcanic vents, and other deep extreme life.

om@umr.edu
2004-Aug-06, 03:42 AM
Originally posted by Algenon the mouse@Aug 6 2004, 12:48 AM
I understand that these gamma rays also can sterilize a planet of life.
Algenon,

Given the proximity and violent, uncertain nature of the Sun, the greatest threat to sterilize this planet of life is probably next door.

With kind regards,

Oliver
http://www.umr.edu/~om

Guest_StarLab
2004-Aug-06, 01:35 PM
Oops. Sorry. Forgot to log in. :Aargh!:

Oliver, what are the chances? Until astronomers actually view a main sequence star emitting a GRB - and I'm NOT talking about a birth, or death, but the MIDDLE of its life cycle - then I remain unconvinced, yet uncertain, that our star truly could be an Iron Sun.

om@umr.edu
2004-Aug-06, 06:37 PM
Star-Lab,

I did not mean to imply that the Sun might sterilize (end) life on this planet by emitting a GRB.

Life as we know it is fragile, very dependent on a constant input of energy from the Sun. Recent observations suggest that the Sun may be less constant, and more turbulent and uncertain than anyone had expected.

Thus measurements with the Ulysses spacecraft led Louis Lanzerotti to conclude that:

"No one really knows how it" (the sun's magnetic field) "is formed and why it changes as it does."

http://www.spaceref.com/news/viewpr.html?pid=13022

Likewise, a recently completed survey of stars with few "sunspots", like the Sun during the “Maunder minimum” of the Little Ice Age in Europe and North America, led Geoffrey Marcy to conclude:

"The fact is, we still don't understand what's going on in our sun, how magnetic fields generate the 11-year solar cycle, or what caused the magnetic Maunder minimum."

http://www.berkeley.edu/news/media/release...1_maunder.shtml (http://www.berkeley.edu/news/media/releases/2004/06/01_maunder.shtml)

Thus, GRBs are probably not the greatest threat to "Life". We may be on the brink of "knowing that we do not know" the source of energy that drives that unnatural process.

With kind regards,

Oliver
http://www.umr.edu/~om