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标题：The Many-faceted Light Curves of Young Disk-bearing Stars in Upper Sco –– Oph Observed by K2 Campaign 2
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作者：Ann Marie Cody ; Lynne A. Hillenbrand
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：156
期号：2
页码：1-16
DOI：10.3847/1538-3881/aacead
语种：English
出版社：American Institute of Physics
摘要：The K2 Mission has photometrically monitored thousands of stars at high precision and cadence in a series of ∼80-day campaigns focused on sections of the ecliptic plane. During its second campaign, K2 targeted over 1000 young stellar objects (YSOs) in the ∼1–3 Myr ρOphiuchus and 5–10 Myr Upper Scorpius regions. From this set, we have carefully vetted photometry from WISE and Spitzer to identify those YSOs with infrared excess indicative of primordial circumstellar disks. We present here the resulting comprehensive sample of 288 young disk-bearing stars from B through M spectral types and analysis of their associated K2 light curves. Using statistics of periodicity and symmetry, we categorize each light curve into eight different variability classes, notably including “dippers” (fading events), “bursters” (brightening events), stochastic, and quasi-periodic types. Nearly all (96%) of disk-bearing YSOs are identified as variable at 30-minute cadence with the sub-1% precision of K2. Combining our variability classifications with (circum)stellar properties, we find that the bursters, stochastic sources, and the largest amplitude quasi-periodic stars have larger infrared colors, and hence stronger circumstellar disks. They also tend to have larger Hα equivalent widths, indicative of higher accretion rates. The dippers, on the other hand, cluster toward moderate infrared colors and low Hα. Using resolved disk observations, we further find that the latter favor high inclinations, except for a few notable exceptions with close to face-on disks. These observations support the idea that YSO time-domain properties are dependent on several factors, including accretion rate and view angle.
关键词：accretion;accretion disks;circumstellar matter;protoplanetary disks;stars: pre-main sequence;stars: variables: T Tauri;Herbig Ae/Be;starspots