Systematic Multiepoch Monitoring of LkCa 15: Dynamic Dust Structures on Solar System Scales
Systematic Multiepoch Monitoring of LkCa 15: Dynamic Dust Structures on Solar System Scales
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DOI：
10.3847/1538-4357/ace16c
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发表时间：
2023-06
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影响因子：
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通讯作者：
S. Sallum;J. Eisner;A. Skemer;R. Murray-Clay
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作者：
S. Sallum;J. Eisner;A. Skemer;R. Murray-Clay
我们展示了 LkCa 15 的最高角分辨率红外监测，LkCa 15 是一个拥有过渡盘的年轻太阳类似物。该系统一直是从毫米到光学的一系列直接成像研究的主题，这些研究揭示了多个原行星盘环以及在红外连续发射中检测到的三个轨道原行星候选者（其中一个在 Hα 处同时看到）。我们从 2014 年到 2020 年使用高角分辨率红外成像来系统地监测这些红外信号并确定它们的物理起源。我们发现三颗自发光原行星无法解释红外源的位置演化，因为较长时间的基线图像缺乏伴星所预期的相干轨道运动。然而，数据仍然强烈倾向于时变形态，而静态散射光盘模型无法再现该形态。多历元观测表明，存在复杂且动态的子结构，它们在~20 au处移动穿过盘的前向散射侧，或者通过较近的物质快速变化的阴影。我们探讨了之前对一个候选者的 Hα 检测是否与这种情况不一致，并在此过程中针对在前向散射光附近检测到的 Hα 过量情况开发了一种分析信噪比惩罚。在这些新的噪声考虑下，Hα 检测与前向散射并不强烈不一致，这使得动态 LkCa 15 圆盘成为红外和 Hα 数据的自然解释。
We present the highest-angular-resolution infrared monitoring of LkCa 15, a young solar analog hosting a transition disk. This system has been the subject of a number of direct-imaging studies from the millimeter through the optical, which have revealed multiple protoplanetary disk rings as well as three orbiting protoplanet candidates detected in infrared continuum emission (one of which was simultaneously seen at Hα). We use high-angular-resolution infrared imaging from 2014 to 2020 to systematically monitor these infrared signals and determine their physical origin. We find that three self-luminous protoplanets cannot explain the positional evolution of the infrared sources since the longer time baseline images lack the coherent orbital motion that would be expected for companions. However, the data still strongly prefer a time-variable morphology that cannot be reproduced by static scattered-light disk models. The multiepoch observations suggest the presence of complex and dynamic substructures moving through the forward-scattering side of the disk at ∼20 au or quickly varying shadowing by closer-in material. We explore whether the previous Hα detection of one candidate would be inconsistent with this scenario and in the process develop an analytical signal-to-noise penalty for Hα excesses detected near forward-scattered light. Under these new noise considerations, the Hα detection is not strongly inconsistent with forward scattering, making the dynamic LkCa 15 disk a natural explanation for both the infrared and Hα data.