利用K2发现新的北斗星：金牛T星内盘区的一个窗口
Discovery of New Dipper Stars with K2: A Window into the Inner Disk Region of T Tauri Stars
摘要：
近年来，一种新的年轻恒星天体被定义，称为勺形天体，在那里可以观察到大的瞬时通量下降。这些下降太大，不能归因于恒星的变化，持续数小时到数天，可以减少10- 50%的恒星通量。这种变化被归因于星周盘内缘附近的翘曲或吸积柱的掩星。在这里，我们使用随机森林分类器进行监督机器学习，在K2战役2数据中发现了上天蝎座关联和$ρ$蛇夫座云复合体中的95个dipper。我们还提出了30个YSO，表现出明亮的事件的顺序天，被称为突发事件。并非所有的勺星和爆发星都是已知的成员，但它们都表现出红外线过剩，并与属于两个年轻恒星形成区中的任何一个相一致。我们发现21.0 $\pm$ 5.5%的恒星与磁盘是勺为两个地区的组合。我们的整个北斗样本只包括晚型（KM）恒星，但我们表明，偏见限制北斗发现早期光谱类型。使用北斗星特性作为替代，我们发现内盘边缘的温度与类似和早期类型恒星的干涉测量结果一致。
英文摘要：
In recent years a new class of Young Stellar Object has been defined, referred to as dippers, where large transient drops in flux are observed. These dips are too large to be attributed to stellar variability, last from hours to days and can reduce the flux of a star by 10-50\%. This variability has been attributed to occultations by warps or accretion columns near the inner edge of circumstellar disks. Here we present 95 dippers in the Upper Scorpius association and $ρ$ Ophiuchus cloud complex found in K2 Campaign 2 data using supervised machine learning with a Random Forest classifier. We also present 30 YSOs that exhibit brightening events on the order of days, known as bursters. Not all dippers and bursters are known members, but all exhibit infrared excesses and are consistent with belonging to either of the two young star forming regions. We find 21.0 $\pm$ 5.5\% of stars with disks are dippers for both regions combined. Our entire dipper sample consists only of late-type (KM) stars, but we show that biases limit dipper discovery for earlier spectral types. Using the dipper properties as a proxy, we find that the temperature at the inner disk edge is consistent with interferometric results for similar and earlier type stars.
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