THE ASTRALUX MULTIPLICITY SURVEY: EXTENSION TO LATE M-DWARFS
THE ASTRALUX MULTIPLICITY SURVEY: EXTENSION TO LATE M-DWARFS
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DOI：
10.1088/0004-637x/789/2/102
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发表时间：
2014-06
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影响因子：
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通讯作者：
M. Janson;C. Bergfors;W. Brandner;N. Kudryavtseva;F. Hormuth;S. Hippler;T. Henning
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文献类型：
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作者：
M. Janson;C. Bergfors;W. Brandner;N. Kudryavtseva;F. Hormuth;S. Hippler;T. Henning
低质量恒星之间多重性的分布是了解恒星和褐矮星形成的一个关键问题，最近的调查已经获得了足够大的附近低质量恒星样本，可以从统计上以良好的准确性研究这个问题。在此之前，我们已经提出了一个多重性研究的700早期/中期M型恒星观测与AstraLux高分辨率幸运成像相机。本文通过对286颗邻近的中晚期M型星的研究，扩展了M型星多重性的研究，填补了我们以前的研究与棕矮星多重性研究之间的差距。大多数目标都被观察了不止一次，这使我们能够评估共同的自行运动，以确认伴侣关系。我们在66个系统中检测到68个确认或可能的同伴，其中41个以前未被发现。探测器的分辨率可低至仪器的100 μ s。AstraLux灵敏度范围内的原始多重性为17.9%，导致总多重性分数为21%-27%，具体取决于质量比分布，这与平坦下降至<0.4的质量比一致，但不能严格限制在该值以下。半长轴分布可以用对数正态函数很好地表示，μa = 0.78，σa = 0.47，比类太阳样本更窄，在更小的分离处达到峰值。这与平均半长轴从最高质量双星到褐矮星双星的稳定下降是一致的。
The distribution of multiplicity among low-mass stars is a key issue to understanding the formation of stars and brown dwarfs, and recent surveys have yielded large enough samples of nearby low-mass stars to study this issue statistically to good accuracy. Previously, we have presented a multiplicity study of ∼700 early/mid M-type stars observed with the AstraLux high-resolution Lucky Imaging cameras. Here, we extend the study of multiplicity in M-type stars through studying 286 nearby mid/late M-type stars, bridging the gap between our previous study and multiplicity studies of brown dwarfs. Most of the targets have been observed more than once, allowing us to assess common proper motion to confirm companionship. We detect 68 confirmed or probable companions in 66 systems, of which 41 were previously undiscovered. Detections are made down to the resolution limit of ∼100 mas of the instrument. The raw multiplicity in the AstraLux sensitivity range is 17.9%, leading to a total multiplicity fraction of 21%–27% depending on the mass ratio distribution, which is consistent with being flat down to mass ratios of ∼0.4, but cannot be stringently constrained below this value. The semi-major axis distribution is well represented by a log-normal function with μa = 0.78 and σa = 0.47, which is narrower and peaked at smaller separations than for a Sun-like sample. This is consistent with a steady decrease in average semi-major axis from the highest-mass binary stars to the brown dwarf binaries.