扇贝壳双星系统 DG CVn 的偏振、可变射电辐射
Polarized, variable radio emission from the scallop-shell binary system DG CVn
AI总结：
本文分析 DG CVn 双星系统的射电观测，发现弱偏振宁静辐射与高圆偏振爆发，提出电子回旋脉泽机制，并建议联合观测以探究光学吸收体与射电爆发的关联。
摘要：
DG CVn 是一颗爆发型变星，是已知复合周期变星（即扇贝壳星）样本中距离最近的一员。多年来，这个 M 矮星双星系统在很宽的频率范围内表现出显著的耀发活动。在此，我们介绍了利用 Karl G. Jansky 甚大阵列在 L 波段（中心频率 1.5 GHz）对该恒星系统进行的约 14 小时射电观测的详细分析。在两次各 7 小时的观测中，我们发现了一个宁静的、弱偏振的成分，这可能归因于来自环绕一颗或两颗恒星磁层的非相干回旋同步辐射，同时还发现了多个约 90% 右旋圆偏振的爆发，其中一些持续几分钟，而另一些则更长，约 30 分钟以上。其中一些爆发在频率和时间上表现出漂移，这可能是由波束效应或产生辐射的等离子体运动引起的。我们评估了爆发频率随主周期和次周期可能存在的调制，并讨论了这些爆发的性质，倾向于电子回旋脉泽而非等离子体辐射作为可能的潜在机制。我们将 DG CVn 的动态频谱与其他年轻 M 矮星进行了比较，发现了许多相似之处。需要进行专门的射电/光学同时跟踪观测，以监测长期变率，增加爆发的统计量，从而检验在光学波段探测到的共转吸收体能否驱动观测到的射电辐射，以及射电爆发的发生是否与任一恒星的旋转相位相关。
英文摘要：
DG CVn is an eruptive variable star and represents the closest member of the known sample of complex periodic variables, or scallop-shell stars. Over the years, this M dwarf binary system has shown significant flaring activity at a wide range of frequencies. Here, we present a detailed analysis of $\sim 14$ hours of radio observations of this stellar system, taken with the Karl G.Jansky Very Large Array at band L, centered at 1.5 GHz. In both $7$-hour long observations, we have found a quiescent, weakly polarized component, that could be ascribable to the incoherent, gyro-synchrotron emission coming from the magnetosphere surrounding one or both stars, along with multiple $\sim90\%$ right-circularly polarized bursts, some of which last for a few minutes, while others being longer, $\gtrsim$ 30 minutes. Some of these bursts show a drift in frequency and time, possibly caused due to beaming effects or the motion of the plasma responsible for the emission. We assess the possible modulation of burst frequency with the primary and secondary periods, and discuss the properties of these bursts, favoring electron cyclotron maser over plasma emission as the likely underlying mechanism. We compare DG CVn's dynamic spectrum to other young M dwarfs and find many similarities. A dedicated proper radio/optical simultaneous follow-up is needed to monitor the long-term variability, increase the statistics of bursts, in order to test whether the co-rotating absorbers detected in optical can drive the observed radio emission, and whether the occurrence of radio bursts correlates with the rotational phase of either stars.
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