$ε$ Indi Ba，Bb系统云覆盖的大尺度变化
Large-scale changes of the cloud coverage in the $ε$ Indi Ba,Bb system
摘要：
我们介绍了对附近的褐矮星双星$ε$ Indi Ba，Bb进行14个夜晚的\textit{I}波段光度监测的结果。观察是在2个月内获得的，以1.4分钟的典型高节奏进行的总覆盖时间接近42小时。在仅分离$0.7''$时，我们不解析各个组件，因此有效地将二进制文件视为单个对象。然而，$ε$ Indi Ba（光谱类型T1）是已知最明亮的T型棕矮星，预计将主导光度信号。我们通常在每个单独的观测夜晚都没有发现与目标相关的强烈变化，但在2个月的活动中，平均亮度发生了显著变化-与$0.10$大小相当。这种强烈的变化在至少2天的时间尺度上是明显的。我们没有检测到明确的周期性信号，这表明我们可能正在观察T1褐矮星几乎极点，和数天的平均亮度变化是由云覆盖的大尺度结构的变化引起的。动态云很可能会产生闪电，并获得互补的高节奏\textit{V} -波段和H \textit{$α$}图像，以搜索与随机“罢工”相关的发射特征。“我们报告说，在这两个通带中没有发现目标。
英文摘要：
We present the results of 14 nights of \textit{I}-band photometric monitoring of the nearby brown dwarf binary, $ε$ Indi Ba,Bb. Observations were acquired over 2 months, and total close to 42 hours of coverage at a typically high cadence of 1.4 minutes. At a separation of just $0.7''$, we do not resolve the individual components, and so effectively treat the binary as if it were a single object. However, $ε$ Indi Ba (spectral type T1) is the brightest known T-type brown dwarf, and is expected to dominate the photometric signal. We typically find no strong variability associated with the target during each individual night of observing, but see significant changes in mean brightness - by as much as $0.10$ magnitudes - over the 2 months of the campaign. This strong variation is apparent on a timescale of at least 2 days. We detect no clear periodic signature, which suggests we may be observing the T1 brown dwarf almost pole-on, and the days-long variability in mean brightness is caused by changes in the large-scale structure of the cloud coverage. Dynamic clouds will very likely produce lightning, and complementary high cadence \textit{V}-band and H\textit{$α$} images were acquired to search for the emission signatures associated with stochastic "strikes." We report no positive detections for the target in either of these passbands.
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