Spectrum of cosmic fireballs

Abstract

A progress report on cosmic fireballs is presented. The main new results are: (a) the phenomenon should be almost universal, and most explosive γ-ray sources should show the characteristic fireball spectrum; (b) even if the radiation density is insufficient, pair production in electron-proton or electron-electron scattering might start the fireball; (c) some computed fireball spectra are shown. They all have in common a 1/E low-energy behaviour, a 100 keV flattening, and a ∼0.5 MeV cut-off.