Spectra and equitemporal surfaces of the photosphere of the ultrarelativistic shell as applied to Gamma-ray bursts

Abstract

We study the radiation of the ultrarelativistic shell in the diffusion approximation, which takes place at the initial stage of a gamma-ray burst. We get the effective temperature, instantaneous and time-integrated spectra for the parabolic distribution of the initial internal energy of the shell. Also we considered the types of the equitemporal surfaces with a different type of the movement of the shell.