Sub-mm VLBI observations of the event horizon of the super-massive black hole at the Galaxy center

为了构建能够分辨超大质量黑洞视界尺度的亚毫米级VLBI阵列，我们在智利为ASTE望远镜配备了亚毫米级VLBI观测所需的仪器。在此基础上，我们首次开展了包括智利站在内的亚毫米级VLBI国际观测。虽然智利基线还没有探测到条纹，结果只提供了源通量和亮度温度的上限，但基于其他基线的观测，我们已经在几十个视界的尺度上探测到Sgr A的短期变化，为我们了解超大质量黑洞附近的详细结构提供了新的线索。

In order to build a sub-mm VLBI array which is capable of resolving the event horizon scale of super-massive black holes, we have equipped ASTE telescope in Chile with instruments necessary for conducting sub-mm VLBI observations. Based on this, we have conducted international sub-mm VLBI observations including Chilean station for the first time. While fringes are yet to be detected with Chilean baselines and the results only provide an upper limit on the flux and brightness temperature of the source, based on observations with other baselines we have detected short-term variability of Sgr A in a scale of a few tens of the event horizon, providing us a new clue to understand detailed structures in the vicinity of the super-massive black hole.