GRB 090227B: a First Example of a Genuine Short GRB

MUCCINO, M.; BIANCO, C. L.; IZZO, L.; PENACCHIONI, A. V.; RUFFINI, R.

Pekin

Congreso; 3rd Galileo?Xu Guangqi Meeting; 2013

In the context of the Fireshell scenario Gamma-Ray Bursts (GRBs) find a natural explanation in the values of three main parameters: the energy of the emitting e± plasma Etot, the baryon load B, and the density of the Circum-Burst Medium (CBM) n . e± CBMFor B􏰅10−5, the GRB consists of a spike-like emission without any afterglow: a genuine short burst. GRB 090227B is the first recognized genuine short GRB. Its analysis reveals that the transparency emission is not a pure thermal process, owing to a non-gradual transition between the optically thick and the optically thin phases. Within our theory we have recovered the original thermal spectrum of the e± plasma, namely the effective Black body (BB); we indeed have determined the parameters of the Fireshell model, including the redshift. Setting a baryon load B=10−6, we obtain the effective tempera- ture kT =(719.3±48.5) keV, the Lorentz factor at transparency Γ=12852, and the total energy Etot=(1.13±0.12)×1054 erg. The estimated redshift is z=4.07±0.36.