A structured jet explains the extreme GRB 221009A
Kouveliotou, Chryssa; Buckley, David A. H.; Hammerstein, Erica; Andreoni, Igor; Kasliwal, Mansi M.; Watson, Alan M.; Anand, Shreya; Ryan, Geoffrey; O'Connor, Brendan; Troja, Eleonora; Dichiara, Simone; van der Horst, Alexander J.; Butler, Nathaniel R.; Lee, William H.; Srinivasaragavan, Gokul P.; Durbak, Joseph; Beniamini, Paz; Ricci, Roberto; Gill, Ramandeep; Granot, Jonathan; van Eerten, Hendrik; Lipunov, Vladimir; Gillanders, James H.; Moss, Michael; Becerra, Rosa L.; Cenko, Stephen B.; Chasovnikov, Aristarkh; Francile, Carlos; Kutyrev, Alexander S.; Topolev, Vladislav; Yang, Yuhan; Zhirkov, Kirill
Abstract
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 ≈ 10 55 erg) and proximity ( z ≈ 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 ≈ 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. The afterglow of GRB 221009A implies a shallow structured jet is produced in the most powerful stellar explosions.