Radiation diffusion in a ultra-relativistic expanding shell in relation to gamma-ray bursts

The present-day observational data obtained by satellite observatories cover seven decades of gamma-ray energy, and there is no universal general model describing the formation spectrum. Therefore, it important to describe initial stages radiation propagation in an ultrarelativistically expanding shell. aim this study was obtain equations a relativistically shell diffusion limit, solve them for natural data, apply results bursts. following were obtained: stage burst photon-thin case can be described shell; time interval at which still possible use approximation increases with increasing depth inside quadratically; value beyond used increases, intensity decreases approaches; during main shell, suitable most jet. parameters emission are close ones short