GRB 221009A Gamma Rays from the Radiative Decay of Heavy Neutrinos?
Alexei Smirnov, Andreas Trautner
Abstract
We consider a mechanism that causes a decrease in the attenuation of high energy gamma-ray flux from gamma ray burst GRB 221009A. The mechanism is based on the existence of a heavy ${m}_{N}\ensuremath{\sim}(0.1\ensuremath{-}1)\text{ }\text{ }\mathrm{MeV}$ mostly sterile neutrino $N$ which mixes with active neutrinos. $N$'s are produced in the gamma-ray burst (GRB) in $\ensuremath{\pi}$ and $K$ decays via mixing with ${\ensuremath{\nu}}_{\ensuremath{\mu}}$. They undergo the radiative decay $N\ensuremath{\rightarrow}\ensuremath{\nu}\ensuremath{\gamma}$ on the way to Earth. The usual exponential attenuation of gamma rays is lifted to an attenuation inverse in the optical depth. Various restrictions on this scenario are discussed. We find that the high energy $\ensuremath{\gamma}$ events at 18 TeV can be explained if (i) the GRB active neutrino fluence is close to the observed limit, (ii) the branching ratio of $N\ensuremath{\rightarrow}\ensuremath{\nu}\ensuremath{\gamma}$ is at least of the order 10%.