Extreme superluminal expansion traces an ultra-narrow GRB jet across relativistic regimes
Researchers used high-resolution VLBI observations and multi-wavelength data to study GRB 221009A's ultra-narrow jet evolution. The study found a two-stage size growth pattern and constrained the initial half-opening angle to be extremely narrow, between 0.01 and 0.03 radians, providing crucial insights into relativistic jet dynamics.