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Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
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2011 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 729, no 2, 114- p.Article in journal (Refereed) Published
Abstract [en]

We report on the observation of the bright, long gamma-ray burst, GRB 090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB 090926A shares several features with other bright LAT bursts. In particular, it clearly shows a short spike in the light curve that is present in all detectors that see the burst, and this in turn suggests that there is a common region of emission across the entire Fermi energy range. In addition, while a separate high-energy power-law component has already been observed in other gamma-ray bursts, here we report for the first time the detection with good significance of a high-energy spectral break (or cutoff) in this power-law component around 1.4 GeV in the time-integrated spectrum. If the spectral break is caused by opacity to electron-positron pair production within the source, then this observation allows us to compute the bulk Lorentz factor for the outflow, rather than a lower limit.

Place, publisher, year, edition, pages
2011. Vol. 729, no 2, 114- p.
Keyword [en]
gamma-ray burst: individual (GRB 090926A)
National Category
Physical Sciences Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-69463DOI: 10.1088/0004-637X/729/2/114ISI: 000288608700037OAI: diva2:476907
authorCount :191Available from: 2012-01-12 Created: 2012-01-12 Last updated: 2012-01-12Bibliographically approved

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Axelsson, MagnusConrad, JanGarde, Maja LlenaRipken, JoachimYang, Zhaoyu
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Department of AstronomyThe Oskar Klein Centre for Cosmo Particle Physics (OKC)Department of Physics
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