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GRB 090902B: Afterglow Observations and Implications

Pandey, SB, Swenson, CA, Perley, DA, Guidorzi, C, Wiersema, K, Malesani, D, Akerlof, C, Ashley, MCB, Bersier, D, Cano, Z, Gomboc, A, Ilyin, I, Jakobsson, P, Kleiser, IKW, Kobayashi, S, Kouveliotou, C, Levan, AJ, McKay, TA, Melandri, A, Mottram, CJ , Mundell, CG, O'Brien, PT, Phillips, A, Rex, JM, Siegel, MH, Smith, RJ, Steele, IA, Stratta, G, Tanvir, NR, Weights, D, Yost, SA, Yuan, F and Zheng, W (2010) GRB 090902B: Afterglow Observations and Implications. The Astrophysical Journal, 714 (1). pp. 799-804. ISSN 1538-4357

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The optical-infrared afterglow of the Large Area Telescope (LAT)-detected long-duration burst, GRB 090902B, has been observed by several instruments. The earliest detection by ROTSE-IIIa occurred 80 minutes after detection by the Gamma-ray Burst Monitor instrument on board the Fermi Gamma-Ray Space Telescope, revealing a bright afterglow and a decay slope suggestive of a reverse shock origin. Subsequent optical-IR observations followed the light curve for 6.5 days. The temporal and spectral behavior at optical-infrared frequencies is consistent with synchrotron fireball model predictions; the cooling break lies between optical and XRT frequencies ~1.9 days after the burst. The inferred electron energy index is p = 1.8 ± 0.2, which would however imply an X-ray decay slope flatter than observed. The XRT and LAT data have similar spectral indices and the observed steeper value of the LAT temporal index is marginally consistent with the predicted temporal decay in the radiative regime of the forward shock model. Absence of a jet break during the first 6 days implies a collimation-corrected γ-ray energy E γ > 2.2 × 1052 erg, one of the highest ever seen in a long-duration gamma-ray bursts. More events combining GeV photon emission with multiwavelength observations will be required to constrain the nature of the central engine powering these energetic explosions and to explore the correlations between energetic quanta and afterglow emission.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Q Science > QD Chemistry
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society
Related URLs:
Date Deposited: 09 Feb 2017 09:53
Last Modified: 20 Apr 2022 09:34
DOI or ID number: 10.1088/0004-637X/714/1/799
URI: https://researchonline.ljmu.ac.uk/id/eprint/5478
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