GAMMA-RAY BURST SPECTRUM WITH DECAYING MAGNETIC FIELD
GAMMA-RAY BURST SPECTRUM WITH DECAYING MAGNETIC FIELD
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DOI：
10.1088/0004-637x/780/1/12
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发表时间：
2013-10
期刊：
影响因子：
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通讯作者：
Xiao-Hong Zhao;Zhuo Li;Xuewen Liu;Bin-Bin Zhang-Bin;J. Bai;P. Mészáros
中科院分区：
文献类型：
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作者：
Xiao-Hong Zhao;Zhuo Li;Xuewen Liu;Bin-Bin Zhang-Bin;J. Bai;P. Mészáros
在γ射线暴（GRB）的内激波模型中，由于下游磁场（MF）中快冷电子的同步辐射谱太软，不能产生低能斜率的GRB谱。然而，MF可能会随着与激波阵面的距离而向下游衰减。在这里，我们表明，同步辐射光谱变得更难，如果电子在衰减MF进行同步辐射和逆康普顿冷却。为了使这一点与具有低能斜率νFν ν τ ν的典型GR B谱相一致，冲击后MF衰变时间必须与体电子的冷却时间相当（对应于MF衰变长度通常为100 ~ 105趋肤深度）;在MF衰变时间之后，逆康普顿冷却应该占主导地位;和/或MF衰变的共动时间大致为B t-1.5。一个内激波同步加速器模型和一个衰减的MF可以解释大多数低能斜率不大于ν4/3的伽玛暴。
In the internal shock model for gamma-ray bursts (GRBs), the synchrotron spectrum from the fast cooling electrons in a homogeneous downstream magnetic field (MF) is too soft to produce the low-energy slope of GRB spectra. However, the MF may decay downstream with distance from the shock front. Here we show that the synchrotron spectrum becomes harder if electrons undergo synchrotron and inverse-Compton cooling in a decaying MF. To reconcile this with the typical GRB spectrum with low-energy slope νFν∝ν, the postshock MF decay time must be comparable to the cooling time of the bulk electrons (corresponding to a MF decaying length typically of ∼105 skin depths); that the inverse-Compton cooling should dominate synchrotron cooling after the MF decay time; and/or that the MF decays with comoving time roughly as B∝t−1.5. An internal shock synchrotron model with a decaying MF can account for the majority of GRBs with low-energy slopes not harder than ν4/3.