Neutron starquake models for gamma-ray bursts
Neutron starquake models for gamma-ray bursts
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伽马射线暴的中子星震模型
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
P. Madau
中科院分区：
文献类型：
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作者：
O. Blaes;R. Blandford;P. Goldreich;P. Madau
我们评估 γ 射线爆发的中子星震模型。地壳可以存储的弹性能量足以解释单次爆发中辐射的能量，但不足以提供每颗恒星在其一生中产生的 ≳ 10^6 爆发，因此必须补充。如果剪切应力因脆性断裂而释放，则会辐射地震波。然而，它们不能直接传播到表面，而是暂时被捕获在反射层下方。在反射层和表面之间，波的位移幅度几乎恒定，应变很小。在低频（≾ 10^4 Hz）下，反射与渐逝区相关。在高频（≳ 10^4 Hz）下，反射发生在磁场应力开始主导地壳刚性的地方。恒星表面的震动将地震波与传播到磁层的阿尔芬波耦合在一起。在低频下，耦合系数 T 与磁场 B 的平方成正比，并随波频率 v 的七次方增加。在高频下，T 与 B^(4/7)v^(3/7) 成正比。如果磁场 ≳ 10^(11) G 覆盖至少部分恒星表面，则阿尔文波光度足以为银河 γ 射线爆发提供动力。如果阿尔文波缺乏电荷或者其振幅接近背景磁场，则可能会发生阿尔文波向 γ 射线的转换。
We assess neutron starquake models for γ-ray bursts. The elastic energy the crust can store is sufficient to account for that radiated in a single burst, but it is insufficient to supply the ≳ 10^6 bursts each star produces over its lifetime, and so it must be replenished. Seismic waves are radiated if shear stress is relieved by brittle fracture. However they cannot propagate directly to the surface but are temporarily trapped below a reflecting layer. Between the reflecting layer and the surface the displacement amplitude of the wave is nearly constant and the strain is very small. At low frequencies, ≾ 10^4 Hz, the reflection is associated with an evanescent zone. At high frequencies, ≳ 10^4 Hz, the reflection occurs where the magnetic field stress starts to dominate the crustal rigidity. The shaking of the stellar surface couples the seismic waves to Alfen waves which propagate out into the magnetosphere. At low frequencies, the coupling coefficient, T, is proportional to the square of the magnetic field, B, and increases with the seventh power of the wave frequency, v. At high frequencies, T is proportional to B^(4/7)v^(3/7). Alfven wave luminosities sufficient to power Galactic γ-ray bursts are possible if magnetic fields ≳ 10^(11) G cover at least part of the stellar surface. The conversion of Alfven waves into γ-rays may occur if the waves are charge-starved or if their amplitudes approach that of the background magnetic field.