次相对论质子激发Sgr B2中性铁线的K壳层发射
K-shell Emission of Neutral Iron Line from Sgr B2 Excited by Subrelativistic Protons
摘要：
研究了银河系中心大质量分子云K $α$铁谱线的发射。我们假设目前这种辐射的总通量是由人马座A $^\ast$（Sgr A $^\ast$）过去发射的初级X射线光子产生的时变分量和由恒星吸积产生的质子撞击中心黑洞激发的相对较弱的准定常分量组成。背景辐射水平的估计从上升的6.4千电子伏线强度的方向上的几个分子云，我们解释为一个阶段时，由Sgr A $^\ast$进入这些云喷射的X射线前。在此强度跳跃之前的6.4 keV发射，我们解释为亚相对论性宇宙射线产生的发射。由质子产生的K $α$空位的横截面不同于电子或X射线的横截面。因此，我们期望可以从分析的等效宽度的铁线和宽度的时间变化可以预测的过程中区分。来自云的谱线强度取决于它们与Sgr A $^\ast$的距离和银河系中心附近的空间扩散系数。我们预计，在几年内，相对接近Sgr A $^\ast$的云G1，0.11 $-$ 0.11的谱线强度将从其目前值下降到$\lesssim$ 10%的水平。对于云人马座B2（Sgr B2），情况更加复杂。如果扩散系数$D\gtrsim 10^{27}$ cm $^2$ s $^{-1}$，那么预期的静止通量应该是2000年水平的10%左右。在相反的情况下，来自Sgr B2的谱线强度应该下降到零，因为质子没有到达云。
英文摘要：
We investigated the emission of K$α$ iron line from the massive molecular clouds in the Galactic center (GC). We assume that at present the total flux of this emission consists of time variable component generated by primary X-ray photons ejected by Sagittarius A$^\ast$ (Sgr A$^\ast$) in the past and a relatively weak quasi-stationary component excited by impact of protons which were generated by star accretion onto the central black hole. The level of background emission was estimated from a rise of the 6.4 keV line intensity in the direction of several molecular clouds, that we interpreted as a stage when the X-ray front ejected by Sgr A$^\ast$ entered into these clouds. The 6.4 keV emission before this intensity jump we interpreted as emission generated by subrelativistic cosmic rays there. The cross-section of K$α$ vacancies produced by protons differs from that of electrons or X-rays. Therefore, we expect that this processes can be distinguished from the analysis of the equivalent width of the iron line and time variations of the width can be predicted. The line intensity from the clouds depends on their distance from Sgr A$^\ast$ and the coefficient of spacial diffusion near the Galactic center. We expect that in a few years the line intensity for the cloud G\,0.11$-$0.11 which is relatively close to Sgr A$^\ast$ will decreases to the level $\lesssim$ 10% from its present value. For the cloud Sagittarius B2 (Sgr B2) the situation is more intricate. If the diffusion coefficient $D\gtrsim 10^{27}$ cm$^2$ s$^{-1}$ then the expected stationary flux should be about 10% of its level in 2000. In the opposite case the line intensity from Sgr B2 should drop down to zero because the protons do not reach the cloud.
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