Physics of gamma-ray bursts

Abstract

Attention is given to the accumulating evidence for the view that gamma-ray bursts come from strongly magnetic neutron stars, discussing the physical properties of the emission region and the radiation processes expected in strong magnetic fields, and emphasizing that the observed burst spectra require that the emission region be optically thin. This entails that the energy of the emitting plasma and/or the plasma itself be continuously replenished during a burst, and that the cooling time scale of the emitting plasma be much shorter than the observed duration of the bursts. This characteristic of the cooling time scale implies that the burst intensity and spectrum can vary on extremely short time scales, and that the burst duration must have a separate explanation. It is emphasized that synchrotron emission is favored as the gamma-ray production mechanism; it is the only mechanism capable of satisfying the optical thinness constraint while producing the observed luminosity.