Pulse Width Evolution in Gamma-Ray Bursts: Evidence for Internal Shocks
Pulse Width Evolution in Gamma-Ray Bursts: Evidence for Internal Shocks
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DOI：
10.1086/309260
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发表时间：
1999-10
期刊：
影响因子：
--
通讯作者：
E. Ramirez-Ruiz;E. Fenimore
中科院分区：
文献类型：
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作者：
E. Ramirez-Ruiz;E. Fenimore
许多伽玛射线暴（GRB）的宇宙学模型都设想能量来源是一个灾难性的恒星事件，导致一个相对论膨胀的火球。粒子被认为在冲击时被加速并产生非热辐射。在大多数伽玛暴中观察到的高度可变的时间结构具有显着的约束模型。通过使用不同的方法在时域的统计分析，我们发现，在整个经典的伽玛暴相位的时间历史中的大幅度脉冲的宽度保持显着不变。对于小振幅脉冲也是如此。然而，小脉冲和大脉冲在单个时间历史内不具有相同的脉冲宽度。我们发现脉冲幅度和脉冲宽度之间存在定量关系：较小的幅度峰往往更宽，脉冲宽度遵循指数约为-2.8的幂律。随机选取洛伦兹因子和每层能量模拟的内激波符合幂律关系。这是强有力的定量证据，证明伽玛暴确实是由内部冲击引起的。宽度与强度的关系对最大洛仑兹因子的依赖性提供了一种估计这个难以捉摸的参数的方法。我们观察到的幂律指数表明，Γmax为103。我们还解释了窄的脉冲宽度分布，表明发射时发生的一个壳超过另一个是在一个小范围的距离从中心站点。
Many cosmological models of gamma-ray bursts (GRBs) envision the energy source to be a cataclysmic stellar event leading to a relativistically expanding fireball. Particles are thought to be accelerated at shocks and produce nonthermal radiation. The highly variable temporal structure observed in most GRBs has significantly constrained models. By using different methods of statistical analysis in the time domain, we find that the width of the large-amplitude pulses in GRB time histories remains remarkably constant throughout the classic GRB phase. This is also true for small-amplitude pulses. However, small and large pulses do not have the same pulse width within a single time history. We find a quantitative relationship between pulse amplitude and pulse width: the smaller amplitude peaks tend to be wider, with the pulse width following a power law with an index of about -2.8. Internal shocks simulated by randomly selecting the Lorentz factor and energy per shell are consistent with a power-law relationship. This is strong quantitative evidence that GRBs are indeed caused by internal shocks. The dependency of the width-versus-intensity relationship on the maximum Lorentz factor provides a way to estimate that elusive parameter. Our observed power-law index indicates that Γmax is ≲103. We also interpret the narrowness of the pulse width distribution as indicating that the emission that occurs when one shell overtakes another is produced over a small range of distances from the central site.