The Structure of Gamma Ray Burst Jets

Abstract

Due to relativistic bulk motion, the structure and orientation of gamma-ray burst (GRB) jets have a fundamental role in determining how they appear. The recent discovery of the GW170817 binary neutron star merger and the associated GRB boosted the interest in the modeling and search for signatures of the presence of a (possibly quasi-universal) jet structure in long and short GRBs. In this review, following a pedagogical approach, we summarize the history of GRB jet structure research over the last two decades, from the inception of the idea of a universal jet structure to the current understanding of the complex processes that shape the structure, which involves the central engine that powers the jet and the interaction of the latter with the progenitor vestige. We put some emphasis on the observable imprints of jet structure on prompt and afterglow emission and on the luminosity function, favoring intuitive reasoning over technical explanations.

A simple fully conformal solution of Einstein's gravitational equations and the comparison of its implications with astrophysical data

“…However, in more distant regions, the detection probability is negatively affected both by the decreasing intensity of the sources and by their more difficult localization in an extremely increasing volume. In the Gaussian angular distribution of the intensity of narrow γ-ray bursts [27], the minimum measurable intensity Cmin determines the edge of the Gaussian profile, so the effective solid angle detection of the γ -ray burst decreases with distance. This naturally reduces the probability of passage through the ground-based observation point and hence the frequency of detected sources.…”

The Gravitational Wave Universe Toolbox

“…Those GRBs that are further away are much more likely to be observable if their jet points in our line-of-sight; off-axis GRBs are too weak to be observed at such redshifts. BNSs with inclination angles below ∼15 • should be prioritised, as this is the typical width of a jet opening angle (Sarin et al 2022;Fong et al 2015;Salafia & Ghirlanda 2022).…”

“…-We employed the top-hat jet model in this study, and a nested wider and less energetic top-hat jet to mimic the off-axis emissions. With increasing evidences, people now believe the jet of GRB should be structured (Salafia & Ghirlanda 2022). Our methodology is compatible with a structured jet, by substituting the top-hat function Π(Ω) in the emissivity with a more general continuous angular distribution.…”

The statistical characteristics of the prompt emission lightcurves of gamma‐ray bursts

“…GRBs are typically classified into long and short categories based on their duration of the prompt emission (Kouveliotou et al 1993). The prompt emission lightcurves are thought as the firsthand information of the GRBs, the morphological features of the lightcurves could imply the underlying physics of the radiation mechanisms (Beniamini & Granot 2016; Parsotan & Ito 2022) as well as some other aspects of GRBs (Dai et al 2017), such as central engine (Gao et al 2023), the outflow composition (Bromberg et al 2015), the structures of the relativistic jets (Salafia & Ghirlanda 2022), progenitor models (Camisasca et al 2023), etc. Zhao & Tang (2022) fitted the pulses of nine short GRB lightcurves with the fast‐rising and exponential decaying (FRED) model (Norris et al 1996), they got a correlation between the rise time $$$ {T}_{\mathrm{rise}} $$$ and the full width of half maximum height $$$ \mathrm{FWHM} $$$, that is, $$$ \mathrm{FWHM}\propto {T}_{\mathrm{rise}}^{0.78\pm 0.15} $$$.…”