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Early afterglows from radially structured outflows and the application to X-ray shallow decays
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作者 Xue-Wen Liu Xue-Feng Wu +1 位作者 Yuan-Chuan Zou Tan Lu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2009年第8期911-920,共10页
In the fireball model, it is more physically realistic that ganuna-ray burst (GRB) ejecta have a range of bulk Lorentz factors (assuming M ∝ Г^-8). The low Lorentz factor part of the ejecta will catch up with th... In the fireball model, it is more physically realistic that ganuna-ray burst (GRB) ejecta have a range of bulk Lorentz factors (assuming M ∝ Г^-8). The low Lorentz factor part of the ejecta will catch up with the high Lorentz factor part when the latter is decelerated by the surrounding medium to a comparable Lorentz factor. Such a process will develop a long-lasting weak reverse shock until the whole ejecta are shocked. Meanwhile, the forward shocked materials are gradually supplied with energy from the ejecta that are catching-up, and thus the temporal decay of the forward shock emission will be slower than that without an energy supply. However, the reverse shock may be strong. Here, we extend the standard reverse-forward shock model to the case of radially nonuniform ejecta. We show that this process can be classified into two cases: the thick shell case and the thin shell case. In the thin shell case, the reverse shock is weak and the temporal scaling law of the afterglow is the same as that in Sad & Meszaros (2000). However, in the thick shell case, the reverse shock is strong and thus its emission dominates the afterglow in the high energy band. Our results also show slower decaying behavior of the afterglow due to the energy supply by low Lorentz factor materials, which may help the understanding of the plateau observed in the early optical and X-ray afterglows. 展开更多
关键词 GAMMA-RAYS bursts -- hydrodynamics -- radiation mechanisms nonther- mal -- shock waves
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变质量Birkhoff系统的Lie对称性和非Noether守恒量 被引量:10
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作者 张鹏玉 方建会 《物理学报》 SCIE EI CAS CSCD 北大核心 2006年第8期3813-3816,共4页
采用嵌入质量法建立了变质量系统的Birkhoff方程.根据Lie对称性理论给出了变质量Birkhoff系统的Lie对称性确定方程,得到了系统的Lie对称直接导致非Noether守恒量的存在条件和形成.举例说明结果的应用.
关键词 变质量 BIRKHOFF系统 LIE对称性 非NOETHER守恒量
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