GRB 221009A Gamma Rays from Radiative Decay of Heavy Neutrinos?

We consider a mechanism which allows to decrease attenuation of high energygamma ray flux from gamma ray burst GRB 221009A. The mechanism is based on theexistence of a heavy $m_N\sim0.1\,\mathrm{MeV}$ mostly sterile neutrino $N$which mixes with active neutrinos. $N$'s are produced in GRB in $\pi$ and $K$decays via mixing with $\nu_\mu$. They undergo the radiative decay$N\rightarrow \nu \gamma$ on the way to the Earth. The usual exponentialattenuation of gamma rays is lifted to an attenuation inverse in the opticaldepth. Various restrictions on this scenario are discussed. We find that thehigh energy $\gamma$ events at $18\,\mathrm{TeV}$ and potentially$251\,\mathrm{TeV}$ can be explained if (i) the GRB active neutrino fluence isclose to the observed limit, (ii) the branching ratio of $N\rightarrow \nu\gamma$ is at least of the order 10%.