Probing the Nature of the Weakest Intergalactic Magnetic Fields with the High Energy Emission of Gamma-Ray Bursts

Nov, 2007
19 pages
Published in:
  • Astrophys.J. 682 (2008) 127
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Abstract: (arXiv)
We investigate the delayed, secondary GeV-TeV emission of gamma-ray bursts and its potential to probe the nature of intergalactic magnetic fields. Geometrical effects are properly taken into account for the time delay between primary high energy photons and secondary inverse Compton photons from electron-positron pairs, which are produced in γ\gamma-γ\gamma interactions with background radiation fields and deflected by intervening magnetic fields. The time-dependent spectra of the delayed emission are evaluated for a wide range of magnetic field strengths and redshifts. The typical flux and delay time of secondary photons from bursts at z1z \sim 1 are respectively 108\sim 10^{-8} GeV cm2^{-2} s1^{-1} and 104\sim 10^4 s if the field strengths are 1018\sim 10^{-18} G, as might be the case in intergalactic void regions. We find crucial differences between the cases of coherent and tangled magnetic fields, as well as dependences on the field coherence length.