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Fraser
2005-Sep-12, 05:28 PM
SUMMARY: An Italian team of astronomers have found a gamma ray burst that blew up 12.7 billion light-years away. Since it's so far away, it's also the most powerful blast ever seen. Astronomers have calculated that it exploded with 300 times more energy than our Sun will put out in its entire 10+ billion year lifespan. The blast was discovered by NASA's Swift satellite, which is dedicated to discovering these powerful explosions.

View full article (http://www.universetoday.com/am/publish/distant_gamma-ray_burst_grb_050904_.html)
What do you think about this story? post your comments below.

Don Alexander
2005-Sep-12, 06:16 PM
Welcome back to the GRB Arena!!

Okay, some comments:

First of all, the header is wrong - this is NOT the most powerful GRB ever witnessed (power being "isotropic energy release")!! That is still GRB 990123. It is - by far - the greatest redshift ever measured, though (next best one is 000131 at z = 4.5).

Furthermore, I think this press release is quite audacious.

- MISTICI did not discover the afterglow. That was the FUN GRB collaboration (J. Haislip et al., GCN 3913)
- MISTICI was not the first to posit the high-redshift theory - this was in J. Haislip et al., GCN 3914, further discussed by Dan Reichart, GCN 3915.
- The spectroscopic redshift was nailed to 6.29 +/- 0.01 by the Subaru telescope after more than 3 days, N. Kawai et al., GCN 3937.

What MISTICI did do was to refine the photometric redshift to z = 6.10 +0.37 -0.12, fully conforming to the spectroscopic redshift.

And of course they got a lot of high signal-to-noise afterglow data with the VLT.

This burst was extremely interesting beyond the extreme distance. The gamma-ray emission was almost 500 seconds long (stretched by 1+z = 7.29, of course), and the TAROT and BOOTES robotic telescocopes were on the burst while the gamma-ray emission was still ongoing - they actually got a few data points in the R band, even though this band is extremely flux defincient do to the Lyman forest.

Swift slewed immediately and started taking XRT data quite a bit before the GR emission ceased, seeing several strong X-ray flares, the first one being identlical with the last peak in Gamma-rays.

All in all, this burst was a goldmine for early afterglow physics.

Fraser
2005-Sep-12, 06:25 PM
Oops, I'll fix the title and text. The press release was a little misleading.

gnosys
2005-Sep-12, 07:06 PM
I'm sure you've already caught this: in the article the figure 12.7 million is mentioned twice -- instead of the 12.7 BILLION in the heading, which I assume is correct.

gnosys
2005-Sep-12, 07:07 PM
Sorry, my mistake...

dboyce37
2005-Sep-13, 03:43 AM
How is the distance of this object measured?

Greg
2005-Sep-14, 03:10 PM
For an object this distant essentially the degree of redshift determines the distance. It gets more complicated than that, so I will try to elaborate. Hubble's law directly correlates the distance to an object with its recessional velocity as determined by the redshift. The equation is v=Ho x r where r is distance, Ho is the Hubble constant (20km/sec per million lightyears), and v is recessional velocity otherwise known as doppler redshift. I should also include that the value of the Hubble constant (which is dervied from a best estimate of the size of the universe) is hotly debated even today. There are some who even question the veracity of the doppler effect such as MOND enthusiasts. I will include a link to a site with more detail on this subject below.

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/hubble.html#c1