%0 Journal Article
%T The ultra-long Gamma-Ray Burst 111209A: the collapse of a blue supergiant?
%A B. Gendre
%A G. Stratta
%A J. L. Atteia
%A S. Basa
%A M. Bo£¿r
%A D. M. Coward
%A S. Cutini
%A V. D'Elia
%A E. Howell
%A A. Klotz
%A L. Piro
%J Physics
%D 2012
%I arXiv
%R 10.1088/0004-637X/766/1/30
%X 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.
%U http://arxiv.org/abs/1212.2392v2