A structured jet explains the extreme GRB 221009A

Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars. Among them, GRB 221009A is by far the brightest burst ever observed. Because of its enormous energy (E-iso approximate to 1055 erg) and proximity (z approximate to 0.15), GRB 221009A is an exceptionally rare event that pushes the limits of our theories. We present multiwavelength observations covering the first 3 months of its afterglow evolution. The x-ray brightness decays as a power law with slope approximate to t(-1.66), which is not consistent with standard predictions for jetted emission. We attribute this behavior to a shallow energy profile of the relativistic jet. A similar trend is observed in other energetic GRBs, suggesting that the most extreme explosions may be powered by structured jets launched by a common central engine.

Automated summary

GRB 221009A, the brightest long-duration gamma-ray burst ever observed, displays X-ray brightness that decays as a power law, indicating a shallow energy profile of the relativistic jet. This behavior challenges standard predictions and suggests a common central engine powering the most extreme explosions, as observed in other energetic GRBs.