Inner disk structure of the classical T Tauri star LkCa 15
Inner disk structure of the classical T Tauri star LkCa 15
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DOI：
10.1051/0004-6361/201834263
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发表时间：
2018-11
影响因子：
6.5
通讯作者：
S. Alencar;J. Bouvier;J. Donati;E. Alecian;C. Folsom;K. Grankin;G. Hussain;C. Hill;A. Cody;A. Carmona;C. Dougados;S. Gregory;G. Herczeg;F. M'enard;C. Moutou;L. Malo;M. Takami;the MaTYSSE collaboration
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作者：
S. Alencar;J. Bouvier;J. Donati;E. Alecian;C. Folsom;K. Grankin;G. Hussain;C. Hill;A. Cody;A. Carmona;C. Dougados;S. Gregory;G. Herczeg;F. M'enard;C. Moutou;L. Malo;M. Takami;the MaTYSSE collaboration
上下文磁层吸积已经在具有完整的未演化吸积盘的年轻恒星系统中得到了深入的研究，但对于具有大内腔的过渡盘天体的记录很少。目标。我们的目标是在LkCa 15，一个典型的过渡盘系统的内部尘埃腔，是50 Au宽的中央星星的星盘相互作用和吸积过程的特征。方法.我们获得了准同时测光和spectropolarimetric观测系统在几个旋转周期。我们分析了系统的光变曲线和相关的颜色变化，以及光谱连续谱和线轮廓的变化，推导出吸积流从内盘边缘到中心星星的性质。我们还推导出在恒星表面的磁场测量。结果我们发现，该系统具有磁性，光度和光谱的变化与约5.70天的周期。光变曲线显示出一个周期性的下降，这表明存在一个内部的磁盘弯曲，位于共转半径约0.06 Au的星星。线轮廓的变化和面纱的变化是一致的磁层吸积模型的漏斗流到达高纬度的星星。这就导致在磁极附近产生吸积激波。所有的诊断都指向一个与恒星磁层相互作用的高度倾斜的内盘。结论. LkCa 15在几天到几周的时间尺度上的光谱和光度变化与AA Tau非常相似，AA Tau是周期性杓型的原型。因此，我们认为，变异的起源是一个旋转的磁盘扭曲，位于一个高度倾斜的磁盘靠近星星的内边缘。这与在大尺度上看到的外过渡盘的适度倾斜形成对比，从而为这个行星形成过渡盘系统的内外盘之间的显著不对准提供了证据。
Context. Magnetospheric accretion has been thoroughly studied in young stellar systems with full non-evolved accretion disks, but it is poorly documented for transition disk objects with large inner cavities. Aims. We aim at characterizing the star-disk interaction and the accretion process onto the central star of LkCa 15, a prototypical transition disk system with an inner dust cavity that is 50 au wide. Methods. We obtained quasi-simultaneous photometric and spectropolarimetric observations of the system over several rotational periods. We analyzed the system light curve and associated color variations, as well as changes in spectral continuum and line profile to derive the properties of the accretion flow from the edge of the inner disk to the central star. We also derived magnetic field measurements at the stellar surface. Results. We find that the system exhibits magnetic, photometric, and spectroscopic variability with a period of about 5.70 days. The light curve reveals a periodic dip, which suggests the presence of an inner disk warp that is located at the corotation radius at about 0.06 au from the star. Line profile variations and veiling variability are consistent with a magnetospheric accretion model where the funnel flows reach the star at high latitudes. This leads to the development of an accretion shock close to the magnetic poles. All diagnostics point to a highly inclined inner disk that interacts with the stellar magnetosphere. Conclusions. The spectroscopic and photometric variability on a timescale of days to weeks of LkCa 15 is remarkably similar to that of AA Tau, the prototype of periodic dippers. We therefore suggest that the origin of the variability is a rotating disk warp that is located at the inner edge of a highly inclined disk close to the star. This contrasts with the moderate inclination of the outer transition disk seen on the large scale and thus provides evidence for a significant misalignment between the inner and outer disks of this planet-forming transition disk system.