用Subaru/CIAO对Sgr A* 耀斑的近红外偏振测量
Near-infrared Polarimetry of flares from Sgr A* with Subaru/CIAO
摘要：
我们已经进行了近红外监测观测Sgr A*，银河系中心的无线电源与超大质量黑洞，与近红外相机CIAO和36元自适应光学系统的斯巴鲁望远镜。在2008年5月28日220分钟的观测中，我们观测到了三个Ks波段（2.15微米）的耀斑，并证实耀斑辐射是高度偏振的，支持了近红外辐射的同步辐射性质。偏振度和位置角的明显变化也被检测到：偏振度增加约20%，在耀斑的下降阶段位置角摆动约60 - 70度。通量和偏振度之间的相关性可以很好地解释为耀斑发射来自于围绕Sgr A* 的热点。与文献中的计算进行比较，给出了对围绕Sgr A* 的热点轨道的倾角i的约束，为45 < i < 90度（接近边缘）。
英文摘要：
We have performed near-infrared monitoring observations of Sgr A*, the Galactic center radio source associated with a supermassive black hole, with the near-infrared camera CIAO and the 36-element adaptive optics system on the Subaru telescope. We observed three flares in the Ks band (2.15micron) during 220 min monitoring on 2008 May 28, and confirmed the flare emission is highly polarized, supporting the synchrotron radiation nature of the near-infrared emission. Clear variations in the degree and position angle of polarization were also detected: an increase of the degree of polarization of about 20 %, and a swing of the position angle of about 60 - 70 degrees in the declining phase of the flares. The correlation between the flux and the degree of polarization can be well explained by the flare emission coming from hotspot(s) orbiting Sgr A*. Comparison with calculations in the literature gives a constraint to the inclination angle i of the orbit of the hotspot around Sgr A*, as 45 < i < 90 degrees (close to edge-on).
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