[论文解读] A family portrait of disk inner rims around Herbig Ae/Be stars: Hunting for warps, rings, self shadowing, and misalignments in the inner astronomical units

J. Kluska, Jean-Philippe Berger+26 more|Lirias (KU Leuven)|Apr 3, 2020

Astrophysics and Star Formation Studies参考文献 89被引用 9

一句话总结

利用甚大望远镜干涉仪（VLTI）上的PIONIER进行近红外干涉测量，本研究以毫角秒分辨率实现了对15颗金牛T星/金牛T型变星周围原行星盘内缘的模型无关成像。结果显示，40%的天体表现出中心对称的辐射，30%因倾斜盘面而呈现非对称辐射，27%表现出非轴对称结构，可能具有时间变异性——表明存在翘曲、不稳定性或伴星；同时未检测到内缘之外的延伸辐射。

ABSTRACT

The innermost astronomical unit in protoplanetary disks is a key region for stellar and planet formation, as exoplanet searches have shown a large occurrence of close-in planets that are located within the first au around their host star. We aim to reveal the morphology of the disk inner rim using near-infrared interferometric observations with milli-arcsecond resolution provided by infrared interferometry. We provide reconstructed images of 15 objects selected from the Herbig AeBe survey carried out with PIONIER at the VLTI, using SPARCO. We find that 40% of the systems are centrosymmetric at the angular resolution of the observations. For the rest of the objects, we find evidence for asymmetric emission due to moderate-to-strong inclination of a disk-like structure for 30% of the objects and noncentrosymmetric morphology due to a nonaxisymmetric and possibly variable environment (30%). Among the systems with a disk-like structure, 20% show a resolved dust-free cavity. The image reconstruction process is a powerful tool to reveal complex disk inner rim morphologies. At the angular resolution reached by near-infrared interferometric observations, most of the images are compatible with a centrally peaked emission (no cavity). For the most resolved targets, image reconstruction reveals morphologies that cannot be reproduced by generic parametric models. Moreover, the nonaxisymmetric disks show that the spatial resolution probed by optical interferometers makes the observations of the near-infrared emission sensitive to temporal evolution with a time-scale down to a few weeks. The evidence of nonaxisymmetric emission that cannot be explained by simple inclination and radiative transfer effects requires alternative explanations, such as a warping of the inner disks. Interferometric observations can, therefore, be used to follow the evolution of the asymmetry of those disks at a sub-au scale.

研究动机与目标

• 研究金牛T星/金牛T型变星周围1天文单位以内的原行星盘内缘形态。
• 通过使用模型无关的图像重建技术，克服参数化建模的局限性。
• 检测并表征内盘区域中的非轴对称结构、翘曲、空洞及倾角错位。
• 评估时间变异性与动力学演化对干涉成像重建的影响。
• 探究观测到的非对称性与物理机制（如盘面翘曲、涡旋或伴星）之间的关联。

提出的方法

• 利用甚大望远镜干涉仪（VLTI）上的PIONIER进行近红外多望远镜干涉测量，实现毫角秒级角分辨率。
• 应用半参数化图像重建方法（SPARCO）生成盘内缘的模型无关图像。
• 采用一致的多波段分析框架，在H、K、L、M和N波段上重建并解释图像。
• 结合1.5至13微米波段的可见度与光谱能量分布（SED）拟合，约束尘埃成分、尺寸及矿物学特性。
• 整合GRAVITY的偏振能力，探测散射光并提升内盘区域的对比度。
• 开展时域观测，评估在数周时间尺度上非对称系统的动力学演化。

实验结果

研究问题

• RQ1 通过模型无关成像，金牛T星/金牛T型变星盘内缘的真实形态是什么？
• RQ2 观测到的内盘非对称性在多大程度上源于倾角效应，而非轴对称结构（如翘曲或涡旋）？
• RQ3 在这些盘的最内区（1 AU以内）是否存在可探测的无尘空洞或间隙？
• RQ4 内盘与外盘组件之间的倾角错位在干涉数据中如何表现？能否通过其他手段独立验证？
• RQ5 干涉观测能否在数周时间尺度上解析内盘结构的时间变异性？

主要发现

• 在15个观测系统中，40%（6/15）表现出中心对称的辐射，与中心集中、无空洞的内盘形态一致。
• 30%（5/15）因盘状结构中等至强倾角而呈现非对称辐射，表明存在几何投影效应。
• 27%（4/15）表现出非轴对称、可能具有时间变异性形态，提示存在不稳定性、翘曲或伴星。
• 三个系统（20%）显示出分辨出的无尘空洞，表明最内区可能存在行星形成或清除过程。
• 未检测到内缘之外的延伸辐射，表明内盘结构被限制在数个天文单位以内。
• 在HD100453和HD142527中确认了盘面错位的证据，HD100546中识别出潜在翘曲，HD150193中可能存在错位。