用X射线尘埃散射晕测定天鹅座X-3的距离
Determining the Distance of Cyg X-3 with its X-ray Dust Scattering Halo
摘要：
本文用互相关方法研究了天鹅座X-3的X射线晕。尘埃分布的两个组成部分，需要解释的时间滞后的互相关方法。假设天鹅座OB 2星协（本星系中最丰富的OB星协）的距离为1.7 kpc，另一个均匀的尘埃分布，我们得到天鹅座X-3的距离为$7.2^{+0.3}_{-0.5}$ kpc（68 $%$置信水平）。当使用天鹅座OB 2的距离估计为1.38 kpc或1.82 kpc时，天鹅座X-3的推断距离分别为$3.4^{+0.2}_{-0.2}$ kpc或$9.3^{+0.6}_{-0.4}$ kpc。天鹅座X-3的距离估计不确定性主要与天鹅座OB 2的距离有关，这可能在未来通过高精度天体测量得到改善。这种方法的优点是计算结果对光子能量、尘埃粒子半径、散射截面等的依赖性很弱。
英文摘要：
Using a cross-correlation method, we study the X-ray halo of Cyg X-3. Two components of dust distributions are needed to explain the time lags derived by the cross-correlation method. Assuming the distance as 1.7 kpc for Cygnus OB2 association (a richest OB association in the local Galaxy) and another uniform dust distribution, we get a distance of $7.2^{+0.3}_{-0.5}$ kpc (68$%$ confidence level) for Cyg X-3. When using the distance estimation of Cygnus OB2 as 1.38 kpc or 1.82 kpc, the inferred distance for Cyg X-3 is $3.4^{+0.2}_{-0.2}$ kpc or $9.3^{+0.6}_{-0.4}$ kpc respectively. The distance estimation uncertainty of Cyg X-3 is mainly related to the distance of the Cygnus OB2, which may be improved in the future with high precision astrometric measurements. The advantage of this method is that the result depends weakly on the photon energy, dust grain radius, scattering cross-section and so on.
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