English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The standard model for GRB afterglow emission treats the accelerated electronpopulation as a simple power law, $N(E) \propto E^{-p}$ for $p \gtrsim 2$.However, in standard Fermi shock acceleration a substantial fraction of theswept-up particles do not enter the acceleration process at all. Additionally,if acceleration is efficient then the nonlinear backreaction of acceleratedparticles on the shock structure modifies the shape of the non-thermal tail ofthe particle spectra. Both of these modifications to the standard synchrotronafterglow impact the luminosity, spectra, and temporal variation of theafterglow. To examine the effects of including thermal particles and nonlinearparticle acceleration on afterglow emission, we follow a hydrodynamical modelfor an afterglow jet and simulate acceleration at numerous points during theevolution. When thermal particles are included, we find that the electronpopulation is at no time well-fitted by a single power law, though thehighest-energy electrons are; if the acceleration is efficient, then the powerlaw region is even smaller. Our model predicts hard-soft-hard spectralevolution at X-ray energies, as well as an uncoupled X-ray and optical lightcurve. Additionally, we show that including emission from thermal particles hasdrastic effects (factors of 100 and 30, respectively) on the observed flux atoptical and GeV energies. This enhancement of GeV emission makes afterglowdetections by future $\gamma$-ray observatories, such as CTA, very likely.

Nonlinear particle acceleration and thermal particles in GRB afterglows