GAMMA-RAY BURSTS FROM INTERNAL SHOCKS IN A RELATIVISTIC WIND : TEMPORAL AND SPECTRAL PROPERTIES
GAMMA-RAY BURSTS FROM INTERNAL SHOCKS IN A RELATIVISTIC WIND : TEMPORAL AND SPECTRAL PROPERTIES
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DOI：
10.1046/j.1365-8711.1998.01305.x
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发表时间：
1998-01
影响因子：
4.8
通讯作者：
F. Daigne;R. Mochkovitch
中科院分区：
文献类型：
--
作者：
F. Daigne;R. Mochkovitch
我们建立了伽玛射线爆发模型，其中发射来自相对风中的内部冲击，具有高度不均匀的洛伦兹因子分布。我们使用一种非常简化的方法来跟踪风的演变，在这种方法中，大量的层通过直接碰撞相互作用，但所有的压力波都被抑制了。我们假设磁场和电子洛伦兹因子在激波中达到较大的均分值。由相对论性电子发射的同步加速器光子在观察者坐标系中具有典型的伽玛射线范围内的能量。合成暴被构造为所有内部基本激波贡献的总和，并将其时间和光谱特性与观测结果进行比较。我们再现了脉冲剖面的多样性、单个脉冲的“弗雷德”形状和短时间尺度的可变性。合成脉冲也满足持续时间-硬度关系，单个脉冲在高能处更窄，与观测结果一致。这些结果表明，相对风中的内部激波可能确实是伽马射线暴的起源。然而，一个潜在的问题是耗散过程的效率相对较低。如果相对论性风的动力来自于从圆盘到恒星质量黑洞的吸积，这意味着相当一部分可用能量被注入了风中。
We construct models for gamma-ray bursts where the emission comes from internal shocks in a relativistic wind with a highly non uniform distribution of the Lorentz factor. We follow the evolution of the wind using a very simplified approach where a large number of layers interact by direct collisions but where all pressure waves have been suppressed. We suppose that the magnetic field and the electron Lorentz factor reach large equipartition values in the shocks. Synchrotron photons emitted by the relativistic electrons have a typical energy in the gamma-ray range in the observer frame. Synthetic bursts are constructed as the sum of the contributions from all the internal elementary shocks and their temporal and spectral properties are compared to the observations. We reproduce the diversity of burst profiles, the ``FRED'' shape of individual pulses and the short time scale variability. Synthetic bursts also satisfy the duration-hardness relation and individual pulses are found to be narrower at high energy, in agreement with the observations. These results suggest that internal shocks in a relativistic wind may indeed be at the origin of gamma-ray bursts. A potential problem is however the relatively low efficiency of the dissipation process. If the relativistic wind is powered by accretion from a disc to a stellar mass black hole it implies that a substantial fraction of the available energy is injected into the wind.