论文标题
快速无线电爆发的自调
Self-modulation of Fast Radio Bursts
论文作者
论文摘要
快速无线电爆发（FRB）是进入非线性光学领域的极端天体物理现象，这是激光物理学中开发的领域。经典的非线性效应是自调制。我们使用来自距离来源的距离$ r $的均匀等离子体$ n $的单色线性偏振的GHz波的理想化设置来检查FRB在Circumburst环境中的传播。我们发现，如果平板位于临界半径$ r _ {\ rm crit} \ sim 10^{17}（n/10^2 {\ rm \; cm}^{ - 3} { - 3}）（l/10^{42} {42} {\ rm \; erg; erg; s}^^^^^^^^}^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^{ cm} $，其中$ l $是frb亮度的各向同性。自调调节将爆裂的裂纹横向横向到径向方向。当$ r \ lyssim r _ {\ rm crit} $时，煎饼的横向大小小于菲涅尔刻度。当爆发出口时，煎饼被强烈衍射，煎饼之间的干扰会带有亚GHz带宽的观察强度调制。当$ r \ sim r _ {\ rm crit} $时，煎饼的横向大小与菲涅尔刻度相当，并且衍射的效果较弱。观察到的强度在十微秒的时间表上调节，这对应于煎饼的径向宽度。我们的结果表明，自调制可能导致在FRB中观察到的时间和频率结构。
Fast Radio Bursts (FRBs) are extreme astrophysical phenomena entering the realm of non-linear optics, a field developed in laser physics. A classical non-linear effect is self-modulation. We examine the propagation of FRBs through the circumburst environment using the idealised setup of a monochromatic linearly-polarised GHz wave propagating through a uniform plasma slab of density $N$ at distance $R$ from the source. We find that self-modulation occurs if the slab is located within a critical radius $R_{\rm crit}\sim 10^{17}(N/10^2{\rm\; cm}^{-3})(L/10^{42}{\rm\; erg\; s}^{-1}){\rm\; cm}$, where $L$ is the isotropic equivalent of the FRB luminosity. Self-modulation breaks the burst into pancakes transverse to the radial direction. When $R\lesssim R_{\rm crit}$, the transverse size of the pancakes is smaller than the Fresnel scale. The pancakes are strongly diffracted as the burst exits the slab, and interference between the pancakes produces a frequency modulation of the observed intensity with a sub-GHz bandwidth. When $R\sim R_{\rm crit}$, the transverse size of the pancakes becomes comparable with the Fresnel scale, and the effect of diffraction is weaker. The observed intensity is modulated on a timescale of ten microseconds, which corresponds to the radial width of the pancakes. Our results suggest that self-modulation may cause the temporal and frequency structure observed in FRBs.
