使用甚长基线干涉测量术寻找原恒星的日冕射电发射
Searching for coronal radio emission from protostars using Very-Long-Baseline Interferometry
摘要：
为了直接研究原恒星附近磁场的作用，我们采用甚长基线干涉测量（VLBI）技术，对非热厘米射电辐射进行探测。从技术上讲，这是研究亚AU分辨率日冕发射的唯一可能性。我们对附近的四颗原恒星HL Tau、LDN 1551 IRS5、EC 95和YLW 15进行了VLBI观测，以寻找致密的非热厘米射电辐射。为了获得最大的灵敏度，我们在可能的情况下使用了高灵敏度阵列（HSA），包括甚长基线阵列（VLBA），相控甚大阵列（VLA），以及阿雷西博，格林班克和埃弗尔斯贝格射电望远镜。虽然所有四颗原恒星都在VLA数据中被检测到，但VLBI数据中只检测到一个源（YLW 15 VLA 2）。由于自由-自由吸收，可能取决于源的几何形状，被认为是非检测的可能性。对于YLW 15 VLA 2，精确定轨的前景似乎是好的。
英文摘要：
In order to directly study the role of magnetic fields in the immediate vicinity of protostars, we use Very-Long-Baseline Interferometry (VLBI), aiming at the detection of non-thermal centimetric radio emission. This is technically the only possibility to study coronal emission at sub-AU resolution. We performed VLBI observations of the four nearby protostars HL Tau, LDN 1551 IRS5, EC 95, and YLW 15 in order to look for compact non-thermal centimetric radio emission. For maximum sensitivity, we used the High Sensitivity Array (HSA) where possible, involving the Very Long Baseline Array (VLBA), the phased Very Large Array (VLA), as well as the Arecibo, Green Bank, and Effelsberg radio telescopes. While all four protostars were detected in VLA-only data, only one source (YLW 15 VLA 2) was detected in the VLBI data. The possibility of non-detections due to free-free absorption, possibly depending on source geometry, is considered. For YLW 15 VLA 2, the prospects for an accurate orbit determination appear to be good.
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