Tail emission of prompt gamma-ray burst jets |
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Authors: | Ryo Yamazaki Kenji Toma Kunihito Ioka Takashi Nakamura |
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Institution: | Department of Physics, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan;Department of Earth and Space Science, Osaka University, Toyonaka 560-0043, Japan;Department of Physics, Kyoto University, Kyoto 606-8502, Japan |
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Abstract: | Tail emission of the prompt gamma-ray burst (GRB) is discussed using a multiple emitting sub-shell (inhomogeneous jet, sub-jets or mini-jets) model, where the whole GRB jet consists of many emitting sub-shells. One may expect that such a jet with angular inhomogeneity should produce spiky tail emission. However, we found that the tail is not spiky but is decaying roughly monotonically. The global decay slope of the tail is not so much affected by the local angular inhomogeneity but affected by the global sub-shell energy distribution. The fact that steepening GRB tail breaks appeared in some events prefers the structured jets. If the angular size of the emitting sub-shell is around 0.01–0.02 rad, some bumps or fluctuations appear in the tail emission observed frequently in long GRBs. If the parameter differences of sub-shell properties are large, the tail has frequent changes of the temporal slope observed in a few bursts. Therefore, the multiple emitting sub-shell model has the advantage of explaining the small-scale structure in the observed rapid decay phase. |
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Keywords: | gamma-rays: bursts gamma-rays: theory |
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