Tuesday, May 7, 2013

1305.1261 (Yi-Zhong Fan et al.)

High energy emission of GRB 130427A: evidence for inverse Compton radiation    [PDF]

Yi-Zhong Fan, P. H. T. Tam, Fu-Wen Zhang, Yun-Feng Liang, Hao-Ning He, Bei Zhou, Rui-Zhi Yang, Zhi-Ping Jin, Da-Ming Wei
A nearby super-luminous burst GRB 130427A was simultaneously detected by five $\gamma$-ray space telescopes ({\it Swift}, Fermi-GBM/LAT, Konus-Wind, SPI-ACS/INTEGRAL and AGILE) and by three RAPTOR full-sky persistent monitors. The isotropic $\gamma-$ray energy release is of $\sim 10^{54}$ erg and the absence of a jet break in the X-ray afterglow lightcurve up to $t>7$ days suggests an intrinsic energy release of $> 10^{52}$ erg, rendering it the most powerful explosion among the GRBs with a redshift $z\leq 0.5$. The emission above 100 MeV lasted about one day and four photons are at energies greater than 40 GeV. We show that the count rate of 100 MeV-100 GeV emission may be mainly accounted for by the forward shock synchrotron radiation and the inverse Compton radiation likely dominates at GeV-TeV energies. In particular, an inverse Compton radiation origin is established for the $\sim (95.3,~47.3,~41.4)$ GeV photons arriving at $t\sim (243,~256.3,~610.6)$ s after the trigger of Fermi-GBM. Interestingly, the external-inverse-Compton-scattering of the prompt emission (the second episode, i.e., $t\sim 120-260$ s) by the forward-shock-accelerated electrons is expected to produce a few $\gamma-$rays with a typical energy $\sim 10$ GeV, while five photons above 10 GeV were detected in the same time interval. A possible unified model for the prompt soft $\gamma-$ray, optical and GeV emission of GRB 130427A, GRB 080319B and GRB 090902B is outlined. Implication of the null detection of $>1$ TeV neutrinos from GRB 130427A by IceCube is discussed.
View original: http://arxiv.org/abs/1305.1261

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