利用东亚VLBI网络监测2019年Sgr A* 活动状态期间的大小和通量密度
Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network
摘要：
利用KVN和VERA阵列（KaVA）/东亚VLBI网络（EAVN）的观测资料，对银河系中心超大质量黑洞人马座A*（Sgr A*）进行了研究。特别是在2019年5月13日，Sgr A* 经历了前所未有的明亮近红外（NIR）耀斑;因此，我们在43 GHz（7 mm）处找到了可能的对应物。因此，在2019年5月11日发现了15.4%水平的通量密度的大时间变化，最高通量密度为2.04 Jy。有趣的是，内部尺寸也是可变的，并且面积和长轴尺寸与通量密度显示出>2σ的边缘相关性。因此，我们解释说，43 GHz的发射区域在2019年遵循更大时更亮的关系。讨论了可能的起源与一个弱喷流/外流分量的出现和位置的角度变化的旋转轴的吸积盘的时间。
英文摘要：
In this work, we studied the Galactic Center supermassive black hole (SMBH), Sagittarius A* (Sgr A*), with the KVN and VERA Array (KaVA)/East Asian VLBI Network (EAVN) monitoring observations. Especially on 13 May 2019, Sgr A* experienced an unprecedented bright near infra-red (NIR) flare; so, we find a possible counterpart at 43 GHz (7 mm). As a result, a large temporal variation of the flux density at the level 15.4%, with the highest flux density of 2.04 Jy, is found on 11 May 2019. Interestingly, the intrinsic sizes are also variable, and the area and major-axis size show a marginal correlation with flux density with >2σ. Thus, we interpret that the emission region at 43 GHz follows the larger-when-brighter relation in 2019. The possible origins are discussed with an emergence of a weak jet/outflow component and the position angle change of the rotation axis of the accretion disk in time.
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