GRB 091024A AND THE NATURE OF ULTRA-LONG GAMMA-RAY BURSTS

We present a broadband study of gamma-ray burst (GRB) 091024A within the context of other ultra-long-duration GRBs. An unusually long burst detected by Konus-Wind (KW), Swift, and Fermi, GRB 091024A has prompt emission episodes covering ~1300 s, accompanied by bright and highly structured optical em...

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Bibliographic Details
Published in:The Astrophysical journal 2013-11, Vol.778 (1), p.1-18
Main Authors: Virgili, F J, Mundell, C G, PAL'SHIN, V, Guidorzi, C, Margutti, R, Melandri, A, Harrison, R, Kobayashi, S, CHORNOCK, R, Henden, A
Format: Article
Language:English
Subjects:
AFTERGLOW
Afterglows
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Broadband
Bursting
CORRELATIONS
COSMIC GAMMA BURSTS
COVERINGS
DIAGRAMS
DISTRIBUTION
EMISSION
EVOLUTION
FORECASTING
GAMMA RADIATION
Gamma ray bursts
RED SHIFT
TELESCOPES
VISIBLE RADIATION
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Summary:We present a broadband study of gamma-ray burst (GRB) 091024A within the context of other ultra-long-duration GRBs. An unusually long burst detected by Konus-Wind (KW), Swift, and Fermi, GRB 091024A has prompt emission episodes covering ~1300 s, accompanied by bright and highly structured optical emission captured by various rapid-response facilities, including the 2 m autonomous robotic Faulkes North and Liverpool Telescopes, KAIT, S-LOTIS, and the Sonoita Research Observatory. We also observed the burst with 8 and 10 m class telescopes and determine the redshift to be z = 1.0924 + or - 0.0004. We find no correlation between the optical and gamma -ray peaks and interpret the optical light curve as being of external origin, caused by the reverse and forward shock of a highly magnetized jet (R sub(B) approximately 100-200). Low-level emission is detected throughout the near-background quiescent period between the first two emission episodes of the KW data, suggesting continued central-engine activity; we discuss the implications of this ongoing emission and its impact on the afterglow evolution and predictions. We summarize the varied sample of historical GRBs with exceptionally long durations in gamma-rays ([gap]1000 s) and discuss the likelihood of these events being from a separate population; we suggest ultra-long GRBs represent the tail of the duration distribution of the long GRB population.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/778/1/54