On the magnetization of gamma-ray burst blast waves
May 16, 2013
7 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 435 (2013) 3009
e-Print:
- 1305.3689 [astro-ph.HE]
View in:
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Abstract: (arXiv)
The origin of magnetic fields that permeate the blast waves of gamma-ray bursts (GRBs) is a long-standing problem. The present paper argues that in four GRBs revealing extended emission at >100 MeV, with follow-up in the radio, optical and X-ray domains at later times, this magnetization can be described as the partial decay of the micro-turbulence that is generated in the shock precursor. Assuming that the bulk of the extended emission >100 MeV can be interpreted as synchrotron emission of shock accelerated electrons, we model the multi-wavelength light curves of GRB 090902B, GRB 090323, GRB 090328 and GRB 110731A, using a simplified then a full synchrotron calculation with power-law-decaying microturbulence \epsilon_B \propto t^{\alpha_t} (t denotes the time since injection through the shock, in the comoving blast frame). We find that these models point to a consistent value of the decay exponent -0.5 < \alpha_t < -0.4.Note:
- 8 pages, 4 figures - discussion added, conclusions unchanged - version to appear in MNRAS
References(44)
Figures(4)