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On Septemeber 13, 2008, NASA's Swift detected GRB 080913. Subsequent terrestrial observations by VLT and GROND showed that it was 12.8 Gly distant, making it the most distant GRB observed to date. This stellar explosion occurred around 825 million years after the Big Bang.
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Title: On The Origin Of The Highest Redshift Gamma-Ray Burst GRB 080913
Authors: Krzysztof Belczynski, Dieter H. Hartmann, Chris L. Fryer, Daniel E. Holz, Brian O'Shea

GRB 080913, discovered by SWIFT, is the most distant gamma-ray burst (GRB) known to-date, with a spectroscopically determined redshift of z=6.7. The detection of a burst at such an early epoch of the Universe significantly constrains the nature of GRBs and their progenitors. To evaluate these constraints, we perform population synthesis studies of the formation and evolution of early stars and calculate the resulting formation rates of short- and long-duration GRBs at high redshift. The peak of the GRB rate from Population II stars occurs at z=7 for a model with efficient/fast mixing of metals, while it is found at z=3 for an inefficient/slow metallicity evolution model. We show that for at z=6.7 essentially all GRBs originate from Population II stars, independent of the adopted metallicity evolution model. At this epoch Population III (metal free) stars, representing the very first generation of stars, most likely have already completed their evolution, and Population I stars (representing the present population) have just begun forming. We argue that Population II stars (having small, but non-zero metallicity) are the most likely progenitors of both long GRBs (collapsars) and short GRBs (NS-NS or BH-NS mergers) in the redshift range 6<z<10. Since the predicted rates, after correction for modelling and observational biases, are very similar at these epochs we cannot definitively conclude which of these two progenitor scenarios is more likely in the case of GRB 080913. Further information about these high-z events, such as their spectral energy distribution and host galaxy properties, will be needed for a much larger sample to consolidate the progenitor models considered here.

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Title: GRB 080913 at redshift 6.7
Authors: J. Greiner, T. Kruehler, J.P.U. Fynbo, A. Rossi, R. Schwarz, S. Klose, S. Savaglio, N.R. Tanvir, S. McBreen, T. Totani, B.B. Zhang, X.F. Wu, D. Watson, S.D. Barthelmy, A.P. Beardmore, P. Ferrero, N. Gehrels, D.A. Kann, N. Kawai, A. Kuepcue Yoldas, P. Meszaros, B. Milvang-Jensen, S.R. Oates, D. Pierini, P. Schady, K. Toma, P.M. Vreeswijk, A. Yoldas, B. Zhang, P. Afonso, K. Aoki, D.N. Burrows, C. Clemens, R. Filgas, Z. Haiman, D.H. Hartmann, G. Hasinger, J. Hjorth, E. Jehin, A.J. Levan, E.W. Liang, D. Malesani, T.-S. Pyo, S. Schulze, G. Szokoly, H. Terada, K. Wiersema

We report on the detection by Swift of GRB 080913, and subsequent optical/near-infrared follow-up observations by GROND which led to the discovery of its optical/NIR afterglow and the recognition of its high-z nature via the detection of a spectral break between the i' and z' bands. Spectroscopy obtained at the ESO-VLT revealed a continuum extending down to lambda = 9400 A, and zero flux for 7500 A < lambda<9400 A, which we interpret as the onset of a Gunn-Peterson trough at z=6.695+-0.025 (95.5% conf. level), making GRB 080913 the highest redshift GRB to date, and more distant than the highest-redshift QSO. We note that many redshift indicators which are based on promptly available burst or afterglow properties have failed for GRB 080913. We report on our follow-up campaign and compare the properties of GRB 080913 with bursts at lower redshift. In particular, since the afterglow of this burst is fainter than typical for GRBs, we show that 2m-class telescopes can identify most high-redshift GRBs.

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The Swift space telescope has detected a gamma-ray burst some 12.8 billion light-years from Earth - a record.
These intensely bright but fleeting flashes of very high-energy radiation signal some of the Universe's most violent happenings.
This blast, designated GRB 080913, probably originated in the catastrophic explosion of a massive star.

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NASA's Swift satellite has found the most distant gamma-ray burst ever detected. The blast, designated GRB 080913, arose from an exploding star 12.8 billion light-years away.

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NASA's Swift Catches Farthest Ever Gamma-Ray Burst
NASA's Swift satellite has found the most distant gamma-ray burst ever detected. The blast, designated GRB 080913, arose from an exploding star 12.8 billion light-years away.


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An explosion originating near the edge of the universe has been seen by an orbiting NASA telescope. The burst of gamma rays is the farthest such event ever detected.
The blast, designated GRB 080913, arose from an exploding star 12.8 billion light-years away.

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At 06:46:54 UT, 13th Sept, 2008 the Swift Burst Alert Telescope (BAT) detected  a distant gamma ray burst, GRB 080913.
The reported redshift estimate is  z = 6.44 ± 0.3, which makes it the most distant gamma ray burst ever detected.

Position(2000): RA  = 04h 22m 54.72s,    Dec = -25d 07' 46.0"

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