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Observational Constraints on the Angular and Spectral Distributions of Photons in Gamma-Ray Burst Sources

V. V. Sokolov·G. S. Bisnovatyi-Kogan·V. G. Kurt·Yu. N. Gnedin·Yu. V. Baryshev
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Abstract

The typical spectra of gamma-ray bursts (GRBs) are discussed in the context of the compactness problem for GRB sources and how it is resolved in the popular fireball model. In particular, observational (model-independent) constraints on the collimation of the gamma-rays and the dependence of the collimation angle on the photon energy are considered. The fact that the threshold for the creation of $e^{-}e^{+}$ pairs depends on the angle between the momenta of the annihilating photons in the GRB source provides an alternative solution to the compactness problem. A new approach to explaining GRBs, taking into account the angular dependence for pair creation, is proposed, and the main features of a scenario describing a GRB source with a total (photon) energy smaller or of the order of $10^{49}$ erg are laid out. Thus, we are dealing with an alternative to an ultra-relativistic fireball, if it turns out (as follows from observations) that all "long" GRBs are associated with normal (not peculiar) core-collapse supernovae. The effects of radiation pressure and the formation of jets as a consequence of even a small amount of anisotropy in the total radiation field in a (compact) GRB source are examined in this alternative model. Possible energy release mechanisms acting in regions smaller or of the order of $10^{8}$ cm in size (a compact model for a GRB) are discussed. New observational evidence for such compact energy release in the burst source is considered.

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V. V. Sokolov, G. S. Bisnovatyi-Kogan, V. G. Kurt, Yu. N. Gnedin, Yu. V. Baryshev. 2006-07-28. Observational Constraints on the Angular and Spectral Distributions of Photons in Gamma-Ray Burst Sources. https://doi.org/10.1134/s1063772906080026

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