Deceleration of a Relativistic, Photon-rich Shell: End of Preacceleration, Damping of Magnetohydrodynamic Turbulence, and the Emission Mechanism of Gamma-Ray Bursts
Deceleration of a Relativistic, Photon-rich Shell: End of Preacceleration, Damping of Magnetohydrodynamic Turbulence, and the Emission Mechanism of Gamma-Ray Bursts
复制标题
相对论性富光子壳的减速：预加速的结束、磁流体动力湍流的阻尼以及伽马射线暴的发射机制
DOI：
10.1086/505290
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
C. Thompson
中科院分区：
文献类型：
--
作者：
C. Thompson
我们考虑的相互作用的相对论运动的壳，组成的热光子，一个反向磁场，和一个小的混合物的带电粒子，与密集的沃尔夫-拉叶风。一层薄薄的沃尔夫-拉叶材料被夹带在这个流出的头部;它冷却并变得瑞利-泰勒不稳定，从而提供了一个额外的惯性和可变性来源。穿过前激波的伽马射线给风物质加载了电子-正电子对，并将其推到接近发动机的相对论速度。这就定义了在反向激波通过壳层返回的点上的辐射致密性。我们认为，即时伽马射线发射是由这种外部制动触发，在光学深度~1电子散射。扭转磁流体动力学波由反向磁场的强制重联激发，携带波动电流，并在轻电荷平行运动时在高频下被朗道阻尼。我们发现，加热的电荷冷却主要是由逆康普顿辐射，这是沿着磁场。从喷流底部平流出来的热辐射使粒子冷却。观察到的峰值能量和各向同性的亮度之间的关系，其幅度和缩放再现，如果黑体种子中产生的相对论射流核心，是受开尔文-亥姆霍兹不稳定性与沃尔夫-拉叶包络。在各向同性光度Liso ~ 3 × 1050 ergs-1以下，这个关系被预测为软化。在没有遇到致密恒星包层的外流中，会出现光谱上更硬的爆发。如所观察到的，逆康普顿发射中的尖峰的持续时间在较高频率处较窄。从瞬发γ射线发射到余辉的转变可以用热X射线种子的终止和同步自康普顿发射的开始来解释。
We consider the interaction of a relativistically moving shell, composed of thermal photons, a reversing magnetic field, and a small admixture of charged particles, with a dense Wolf-Rayet wind. A thin layer of Wolf-Rayet material is entrained at the head of this outflow; it cools and becomes Rayleigh-Taylor unstable, thereby providing an additional source of inertia and variability. The gamma rays streaming across the forward shock load the wind material with electron-positron pairs and push it to relativistic speeds close to the engine. This defines a characteristic radiative compactness at the point where the reverse shock has completed its passage back through the shell. We argue that the prompt gamma-ray emission is triggered by this external braking, at an optical depth ~1 to electron scattering. Torsional MHD waves, excited by the forced reconnection of the reversing magnetic field, carry a fluctuating current and are Landau damped at high frequencies on the parallel motion of the light charges. We show that the heated charges cool primilarly by inverse Compton radiation, which is beamed along the magnetic field. Thermal radiation that is advected out from the base of the jet cools the particles. The observed relation between peak energy and isotropic luminosity—both its amplitude and scaling—is reproduced if the blackbody seeds are generated in a relativistic jet core that is subject to Kelvin-Helmholtz instabilities with the Wolf-Rayet envelope. This relation is predicted to soften below an isotropic luminosity Liso ~ 3 × 1050 ergs s-1. Spectrally harder bursts will arise in outflows which encounter no dense stellar envelope. The duration of spikes in the inverse-Compton emission is narrower at higher frequencies, as observed. The transition from prompt gamma-ray emission to afterglow can be explained by the termination of the thermal X-ray seed and the onset of synchrotron-self-Compton emission.