Prompt high-energy emission from gamma-ray bursts in the internal shock model
By Ž. Bošnjak, F. Daigne, G. Dubus. 2008
138 citations recorded by the source corpus.
Context. Gamma-ray bursts (GRB) are powerful, short duration events with a spectral luminosity peaking in the keV-MeV (BATSE) range. The prompt emission is thought to arise from electrons accelerated in internal shocks propagating within a highly relativistic outflow. Aims. The launch of Fermi offers the prospect of observations with unprecedented sensitivity in high-energy (HE, >100 MeV) gammarays. The aim is to explore the predictions for HE emission from internal shocks, taking into account both dynamical and radiative aspects, and to deduce how HE observations constrain the properties of the relativistic outflow. Methods. The prompt GRB emission is modelled by combining a time-dependent radiative code, solving for the electron and photon distributions, with a dynamical code giving the evolution of the physical conditions in the shocked regions of the outflow. Synthetic lightcurves and spectra are generated and compared to observations. Results. The HE emission deviates significantly from analytical estimates, which tend to overpredict the IC component, when the time dependence and full cross-sections are included. The exploration of the parameter space favors the case where the dominant process in the BATSE range is synchrotron emission. The HE component becomes stronger for weaker magnetic fields. The HE lightcurve can display a prolonged pulse duration due to IC emission, or even a delayed peak compared to the BATSE range. Alternatively, having dominant IC emission in the BATSE range requires most electrons to be accelerated into a steep power-law distribution and implies strong second order IC scattering. In this case, the BATSE and HE lightcurves are very similar. Conclusions. The combined dynamical and radiative approach allows a firm appraisal of GRB HE prompt emission. A diagnostic procedure is presented to identify from observations the dominant emission process and derive constrains on the bulk Lorentz factor, particle density and magnetic field of the outflow.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/fae6024b6d2822fc810ca4d89a35f9b2b0326995
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Citations in the corpus
- A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog (2019, background): “…duration: challenges for emission models Synchrotron-Self-Compton (SSC) models for GeV emission is a natural extension of the synchrotron model for keV-MeV emission from GRBs, in the context of the internal shock scenario (see, e.g., Ackermann et al. 2010b; Wang et al. 2009; Bošnjak et al. 2009).”
- The physics of gamma-ray bursts & relativistic jets (2014, background): “These include in- ternal shocks, e.g. Bošnjak et al. (2009), SSC process operating in the external shock (Dermer et al., 2000; Zhang and Mészáros, 2001b) — while the reverse shock is passing through the GRB jet, two SSC processes (in FS and RS, respectively) as well as two cross IC processes (FS…”
- Reconciling observed gamma-ray burst prompt spectra with synchrotron radiation? (2010, methodology): “The full description of this model can be found in Bošnjak et al. (2009).”
- AFTERGLOW OBSERVATIONS OF FERMI LARGE AREA TELESCOPE GAMMA-RAY BURSTS AND THE EMERGING CLASS OF HYPER-ENERGETIC EVENTS (2010, background): “Finally, we add a further note of caution that the derivation of the initial Lorentz factor Γ0 is also subject to significant systematic uncertainties (e.g., Bošnjak et al. 2009).”