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arXiv 1606.03428astro-ph.HE
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部分自吸收射流和Cyg X-1射流的各向异性

Anisotropy of partially self-absorbed jets and the jet of Cyg X-1

Andrzej A. Zdziarski, Debdutta Paul, Ruaraidh Osborne, A. R. Rao

摘要:

本文研究了Blandford & K{<$}nigl提出的部分同步辐射自吸收锥形喷流的角依赖性。我们考虑从一侧或靠近轴线处观察射流,在后一种情况下,从射流顶部或底部观察。我们推导出在这些情况下的通量的解析公式,并找到一个任意角度的数值精确解。我们发现,最大的发射发生时,从顶部轴上的射流,这是对比以前的结果,发现在一些中间的角度和零发射轴上的最大值。然后,我们计算了该模型的喷流对喷流发射的比率,这取决于视角和幂律电子的指数。我们将我们的结果应用到黑洞双星天鹅座X-1。考虑到观测到的$\gtrsim$ 50的喷流与反喷流的流量比和目前对倾角的估计,我们发现喷流速度为$\gtrsim 0.8c$。我们还指出,当考虑投影效应时,射电观测值所隐含的$\lesssim 1^{\rm o}$喷流半张角是以前给出的值的一半。当与现有的$Γ_{\rm j}$估计值相结合时,喷流半开角很低,$\ll 1/Γ_{\rm j}$,并且比在耀变体中观察到的值低得多,除非$Γ_{\rm j}$比目前估计的高得多。

英文摘要:

We study the angular dependence of the flux from partially synchrotron self-absorbed conical jets (proposed by Blandford \& K{ö}nigl). We consider the jet viewed from either a side or close to on axis, and in the latter case, either from the jet top or bottom. We derive analytical formulae for the flux in each of these cases, and find the exact solution for an arbitrary angle numerically. We find that the maximum of the emission occurs when the jet is viewed from top on-axis, which is contrast to a previous result, which found the maximum at some intermediate angle and null emission on-axis. We then calculate the ratio of the jet-to-counterjet emission for this model, which depends on the viewing angle and the index of power-law electrons. We apply our results to the black-hole binary Cyg X-1. Given the jet-to-counterjet flux ratio of $\gtrsim$50 found observationally and the current estimates of the inclination, we find the jet velocity to be $\gtrsim 0.8c$. We also point out that when the projection effect is taken into account, the radio observations imply the jet half-opening angle of $\lesssim 1^{\rm o}$, a half of the value given before. When combined with the existing estimates of $Γ_{\rm j}$, the jet half-opening angle is low, $\ll 1/Γ_{\rm j}$, and much lower than values observed in blazars, unless $Γ_{\rm j}$ is much higher than currently estimated.

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