MULTIWAVELENGTH SIGNATURES OF MAGNETIC ACTIVITY FROM YOUNG STELLAR OBJECTS IN THE LkHα 101 CLUSTER
MULTIWAVELENGTH SIGNATURES OF MAGNETIC ACTIVITY FROM YOUNG STELLAR OBJECTS IN THE LkHα 101 CLUSTER
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LkHα 101 星团中年轻恒星天体磁活动的多波长特征
DOI：
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发表时间：
2008
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影响因子：
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通讯作者：
S. Wolk
中科院分区：
文献类型：
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作者：
R. Osten;S. Wolk
本文描述了我们对LkH α 101星团中年轻天体的多波长观测活动的结果。我们同时进行的X射线和多频射电观测是独一无二的，它同时限制了两个波长的短时间尺度变化，以及限制了年轻恒星射电辐射的热或非热性质。专注于无线电发射的对象和多波长的数据，他们得到的，我们发现，多频无线电数据表明非热发射，即使在对象与红外证据磁盘。我们发现无线电的变化是以几十年、几天和几小时为时间尺度的。大约一半的X射线和无线电探测物体在X射线波长上是可变的，尽管没有大规模的耀斑或大的变化。相对于X射线辐射，变化性似乎是影响射电辐射的更大因素。在射电耀斑的衰变阶段观测到一颗具有盘状红外证据的星星[BW 88] 3。在这个物体和另一个物体（[BW 88] 1）中，我们发现无线电通量和光谱指数之间存在负相关，这与太阳和活跃恒星中的行为形成对比。我们将这种行为解释为由于粒子加速而导致的最硬能量电子的重新布居。一个缺乏红外对应物的射电和X射线源，[BW 88] 1，可能接近亚恒星极限;它的射电性质与其他星团成员相似，但其更高的射电与X射线光度比让人想起附近极低质量恒星/棕矮星的行为。我们发现粒子加速和等离子体加热的签名之间没有对应关系，时间平均和时间变量。在多波长行为中缺乏相关的时间变化，时间平均光度的多波长相关性的崩溃，以及X射线发射物质在无线电波段的光学厚度支持了年轻恒星上的无线电和X射线发射在物理上和/或能量上不同的想法。
We describe the results of our multiwavelength observing campaign on the young stellar objects in the LkHα 101 cluster. Our simultaneous X-ray and multifrequency radio observations are unique in providing simultaneous constraints on short-timescale variability at both wavelengths as well as constraints on the thermal or nonthermal nature of radio emission from young stars. Focussing on radio-emitting objects and the multiwavelength data obtained for them, we find that multifrequency radio data indicate nonthermal emission even in objects with infrared evidence for disks. We find radio variability on timescales of decades, days, and hours. About half of the objects with X-ray and radio detections were variable at X-ray wavelengths, despite lacking large-scale flares or large variations. Variability appears to be a bigger factor affecting radio emission than X-ray emission. A star with infrared evidence for a disk, [BW88] 3, was observed in the decay phase of radio flare. In this object and another ([BW88] 1), we find an inverse correlation between radio flux and spectral index, which contrasts with behavior seen in the Sun and active stars. We interpret this behavior as the repopulation of the hardest energy electrons due to particle acceleration. A radio and X-ray source lacking an infrared counterpart, [BW88] 1, may be near the substellar limit; its radio properties are similar to other cluster members, but its much higher radio to X-ray luminosity ratio is reminiscent of behavior in nearby very low-mass stars/brown dwarfs. We find no correspondence between signatures of particle acceleration and those of plasma heating, both time-averaged and time-variable. The lack of correlated temporal variability in multiwavelength behavior, the breakdown of multiwavelength correlations of time-averaged luminosities, and the optical thickness of X-ray emitting material at radio wavelengths support the idea that radio and X-ray emission on young stars are physically and/or energetically distinct.