Possible effects of pair echoes on gamma-ray burst afterglow emission

Kohta Murase, Bing Zhang, Keitaro Takahashi, Shigehiro Nagataki

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

High-energy emission from gamma-ray bursts (GRBs) is widely expected but had been sparsely observed until recently when the Fermi satellite was launched. If >TeV gamma-rays are produced in GRBs and can escape from the emission region, they are attenuated by the cosmic infrared background photons, leading to regeneration of ∼GeV-TeV secondary photons via inverse-Compton scattering. This secondary emission can last for a longer time than the duration of GRBs, and it is called a pair echo. We investigate how this pair echo emission affects spectra and light curves of high-energy afterglows, considering not only prompt emission but also afterglow as the primary emission. Detection of pair echoes is possible as long as the intergalactic magnetic field (IGMF) in voids is weak. We find (1) that the pair echo from the primary afterglow emission can affect the observed high-energy emission in the afterglow phase after the jet break and (2) that the pair echo from the primary prompt emission can also be relevant, but only when significant energy is emitted in the TeV range, typically. Even non-detections of the pair echoes could place interesting constraints on the strength of IGMF. The more favourable targets to detect pair echoes may be the 'naked' GRBs without conventional afterglow emission, although energetic naked GRBs would be rare. If the IGMF is weak enough, it is predicted that the GeV emission extends to >30-300 s.

Original languageEnglish (US)
Pages (from-to)1825-1832
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume396
Issue number4
DOIs
StatePublished - Jul 1 2009

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afterglows
gamma ray bursts
echoes
magnetic field
energy
magnetic fields
effect
photons
secondary emission
regeneration
light curve
escape
voids
void
energetics
gamma rays
scattering
curves

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Murase, Kohta ; Zhang, Bing ; Takahashi, Keitaro ; Nagataki, Shigehiro. / Possible effects of pair echoes on gamma-ray burst afterglow emission. In: Monthly Notices of the Royal Astronomical Society. 2009 ; Vol. 396, No. 4. pp. 1825-1832.
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Possible effects of pair echoes on gamma-ray burst afterglow emission. / Murase, Kohta; Zhang, Bing; Takahashi, Keitaro; Nagataki, Shigehiro.

In: Monthly Notices of the Royal Astronomical Society, Vol. 396, No. 4, 01.07.2009, p. 1825-1832.

Research output: Contribution to journalArticle

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