JITTER SELF-COMPTON PROCESS: GeV EMISSION OF GRB 100728A

Abstract

Jitter radiation, the emission of relativistic electrons in a random and small-scale magnetic field, has been applied to explain the gamma-ray burst (GRB) prompt emission. The seed photons produced from jitter radiation can be scattered by thermal/nonthermal electrons to the high-energy bands. This mechanism is called jitter self-Compton (JSC) radiation. GRB 100728A, which was simultaneously observed by Swift and Fermi, is a great example to constrain the physical processes of jitter and JSC. In our work, we utilize jitter/JSC radiation to reproduce the multiwavelength spectrum of GRB 100728A. In particular, due to JSC radiation, the powerful emission above the GeV band is the result of those jitter photons in the X-ray band scattered by the relativistic electrons with a mixed thermal-nonthermal energy distribution. We also combine the geometric effect of microemitters to the radiation mechanism, such that the "jet-in-jet" scenario is considered. The observed GRB duration is the result of summing up all of the contributions from those microemitters in the bulk jet.

THE FIRST FERMI -LAT GAMMA-RAY BURST CATALOG

“…This detection confirms the temporal coincidence of the high-energy emission of GRB 100728A with its flaring activity in X-rays, as published in Abdo et al (2011). The implications of the Fermi-LAT observation and the possible connection between the γ -ray emission and the X-ray activity of GRB 100728A have also been discussed in He et al (2012) and Mao & Wang (2012). A 13.54 GeV event with a probability higher than 98% of being associated with the burst is detected ∼90 minutes after the trigger time (see the discussion in Section 4.3.3).…”

The First Fermi LAT Gamma-Ray Burst Catalog

“…This detection confirms the temporal coincidence of the high-energy emission of GRB 100728A with its flaring activity in X-rays, as published in Abdo et al (2011). The implications of the Fermi-LAT observation and the possible connection between the gamma-ray emission and the X-ray activity of GRB 100728A have also been discussed in He et al (2011) and Mao & Wang (2012). A 13.54 GeV event with a probability higher than 98% to be associated with the burst is detected ∼90 minutes after the trigger time (see the discussion in § 4.3.3).…”

Application of Jitter Radiation: Gamma-Ray Burst Prompt Polarization

“…The total observed emission is all of the contributions from these mini-jets. The framework of this scenario was previously built: a small-scale turbulent dynamo was realized by hydrodynamical simulations (Schekochihin et al 2004), jitter radiation was presented (Medvedev 2000(Medvedev , 2006Kelner et al 2013) and examined numerically (Sironi & Spitkovsky 2009;Frederiksen et al 2010), the radiative synthetic spectra from relativistic shocks were also simulated by Martins et al (2009) and Nishikawa et al (2011), the radiation process in a sub-Larmor scale magnetic field was re-examined by Medvedev et al (2011), the electron energy distribution was given by Stawarz & Petrosian (2008) and Giannios & Spitkovsky (2009), turbulence-induced random and small-scale magnetic fields and related jitter radiation for GRB prompt emission were explored by Mao & Wang (2011), this radiation spectrum is fully consistent with the high-frequency spectrum derived from numerical calculations (Teraki & Takahara 2011), and GRB mini-jets were discussed by Mao & Wang (2012). Very recently, some detailed calculations of the microturbulent dynamics behind relativistic shock fronts (Lemoine 2013) and comprehensive analyses of pulses seen in Swift-Burst Alert Telescope GRB lightcurves (Bhatt & Bhattacharyya 2012) also shed light on the physics of jitter radiation, tangled magnetic fields, and relativistic turbulence.…”