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arXiv · 1212.2392

The ultra-long Gamma-Ray Burst 111209A: the collapse of a blue supergiant?

Abstract

We present optical, X-ray and gamma-ray observations of GRB 111209A, at a redshift of z = 0.677. We show that this event was active in its prompt phase for about 25000 seconds, making it the longest burst ever observed. This rare event could have been detected up to z ~ 1.4. Compared to other long GRBs, GRB 111209A is a clear outlier in the energy-fluence and duration plane. The high-energy prompt emission shows no sign of a strong black body component, as expected if the event was caused by a tidal disruption event or a supernova shock breakout. Given the extreme longevity of this event, and a lack of a supernova signature, we propose that GRB 111209A is a relatively rare stellar collapse of a low metallicity blue super giant star. Only this progenitor can supply mass to the central engine over a duration of thousands of seconds. Hence, GRB 111209A could have more in common with population III stellar explosions, rather than normal long gamma ray bursts.

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B. Gendre, G. Stratta, J. L. Atteia, S. Basa, M. Boër, D. M. Coward, S. Cutini, V. D'Elia, E. Howell, A. Klotz, L. Piro. 2013-02-09. The ultra-long Gamma-Ray Burst 111209A: the collapse of a blue supergiant?. https://doi.org/10.1088/0004-637x%2F766%2F1%2F30

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