The spectral properties of gamma-ray bursts: A review of recent developments

Abstract

Recent developments in the spectroscopy of gamma‐ray bursts (GRB) are reviewed. The general question of the validity of the spectral results, particularly with regard to features in the spectrum, is discussed. Confirmations of these spectral features are summarized. Recent results from the KONUS experiments on Venera 13 and 14 are reviewed. The status of models of the continuum spectrum is summarized. A number of different radiation mechanisms appear capable to fitting the data. These include thermal brehmsstrahlung, thermal synchrotron and inverse Compton. Rapid variability of the spectral shape on time scales <0.25 sec. has been reported. The characteristic energy of the spectrum has been observed to vary over nearly an order of magnitude during individual events. A strong correlation between spectral hardness and luminosity has been found. Low‐energy (50 keV) absorption features and high‐energy (400 keV) emission features continue to appear in GRB spectra. Understanding the origin of these lines in the context of the existing continuum models remains a difficult problem.