Light scalar explanation for 18 TeV GRB 221009A

Understand

Recent astrophysical transient Swift J1913.1+1946 may be associated with the $\gamma$-ray burst GRB 221009A.

• The redshift of this event is $z\simeq 0.151$.
• Very high-energy $\gamma$-rays (up to 18 TeV) followed the transient and were observed by LHAASO, additionally Carpet-2 detected a photon-like air shower of 251 TeV.
• Photons of such high energy are expected to readily annihilate with the diffuse extragalactic background light (EBL) before reaching Earth.