Determination of the Angular Distributions of Dynamical and Emission Parameters of Gamma-Ray Burst Relativistic Outflows
Year: 2026
Type: article
Abstract: A previously developed analytical treatment of the larger-angle emission (LAE) model for gamma-ray bursts (GRBs) and afterglows is further developed to include the effect of a fixed magnetic field orientation. This model has the uncanny ability to unify the prompt and delayed emissions and to account easily for the entire diversity of Swift X-ray light curves. The LAE model is applied to seven GRBs (060526, 060614, 060714, 060729, 061007, 061121, 100902, 130427A) with well-sampled 0.3 keV/10 keV Swift X-Ray Telescope (XRT) and optical light curves, displaying well-monitored four phases (GRB, tail, plateau, post-plateau), to illustrate its power and limitations and to determine its five fundamental parameters. Tight constraints are not always obtained from fitting even the best light curves available. The one-and-only core parameter Γ c θ c is determined by the GRB and afterglow temporal milestones (i.e., by the dynamical range of the tail and plateau), and may have a universal value around 3.0, with narrower cores (smaller θ c ) being more relativistic (higher Γ c ). Flat plateaus require an envelope angular structure close to Γ( θ ) ∼ θ −2 . A magnetic field parallel to the direction of the relativistic flow yields more curved prompt/GRB and delayed/afterglow light curves than a perpendicular or isotropic field, with curvature Δ α defined as the difference between the flux asymptotic power-law decay indices at the beginning and end of each phase. The curvature Δ α grb of the GRB light curves arising from the uniform core is set only by the B -field orientation, and a perpendicular or isotropic B field is equally often found, but a parallel field is never identified for the core. The curvature Δ α aglow of the afterglow light curves from the power-law envelope depends on B and three other parameters. The envelope B -field orientation can be identified for only three afterglows, where a parallel B is found.
Source: The Astrophysical Journal
Author: A. Panaitescu
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funder: University of Leicester
OpenAlex ID: W7223130284