两个金牛座T星的相互作用的日冕：类似太阳的盔状流光的第一个观测证据
Interacting coronae of two T Tauri stars: first observational evidence for solar-like helmet streamers
摘要：
年轻的双星系统V773 Tau A表现出持续的射电耀斑活动，从远地点的几mJy逐渐增加到近地点的100 mJy以上。锚定在该系统两颗旋转恒星上的非常大（> 15 R）的磁结构之间的双星间碰撞被认为是这些周期性射电耀斑的起源。磁场结构延伸到几十个恒星半径，这也可以解释观测到的射电耀斑的快速衰减，似乎对应于典型的太阳半开放的相当扩展的磁场配置，称为头盔流光。目标{我们的目标是找到直接的观测证据的假设，太阳一样，日冕拓扑结构。方法{我们使用VLBA和100-m Effelsberg望远镜组成的阵列在8.4 GHz进行了连续7天的VLBI观测。}结果①两种不同的结构出现在这里所提供的无线电图像。它们碰巧与V773 Tau A系统的主星和副星有关。在一幅图像（图2-B）中，两个特征延伸到18 R，几乎平行，揭示了两个相互作用的头盔拖缆的存在。一张由100米埃费尔斯堡望远镜监测到的耀斑后几小时拍摄的图像（图2-E）显示了一个细长的衰落结构，相对于B运行中看到的结构，它基本上发生了旋转。在图2-G中可以看到与另一颗恒星有关的盔状流光的衰变情况。结论{这是第一个直接的证据，表明即使耀斑起源于由于双星间碰撞引起的磁重联，两颗恒星在射电范围内都有各自的结构。这些结构是头盔流光，首次在太阳以外的恒星中观察到。
英文摘要：
Context {The young binary system V773 Tau A exhibits a persistent radio flaring activity that gradually increases from a level of a few mJy at apoastron to more than 100 mJy at periastron. Interbinary collisions between very large (> 15 R) magnetic structures anchored on the two rotating stars of the system have been proposed to be the origin of these periodic radio flares. Magnetic structures extended over tens of stellar radii, that can also account for the observed fast decay of the radio flares, seem to correspond to the typical solar semi-open quite extended magnetic configurations called helmet streamers.} Aims {We aim to find direct observational evidence for the postulated, solar-like, coronal topologies.} Methods {We performed seven-consecutive-day VLBI observations at 8.4 GHz using an array consisting of the VLBA and the 100-m Effelsberg telescope.} Results {Two distintive structures appear in the radio images here presented. They happen to be associated with the primary and secondary stars of the V773 Tau A system. In one image (Fig.2-B) the two features are extended up to 18 R each and are nearly parallel revealing the presence of two interacting helmet streamers. One image (Fig.2-E) taken a few hours after a flare monitored by the 100-m Effelsberg telescope shows one elongated fading structure substantially rotated with respect to those seen in the B run. The same decay scenario is seen in Fig.2-G for the helmet streamer associated with the other star.} Conclusions {This is the very first direct evidence revealing that even if the flare origin is magnetic reconnection due to interbinary collision, both stars independently emit in the radio range with structures of their own. These structures are helmet streamers, observed for the first time in stars other than the Sun.}
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