与盖亚DR2在Sco-Cen OB协会中搜寻恒星飞掠
Search for Stellar Flybys in the Sco-Cen OB Association with the Gaia DR2
摘要：
对碎片盘的高对比度成像研究表明，其形态有很大的多样性，包括大规模的不对称性。涉及恒星飞掠的理论，引力扰动的外部来源，为这些形态变化的起源提供了一个合理的解释。我们的研究是一个实验，以获得经验证据，一直缺乏从这些理论。我们探索这种模式，使用天体测量和径向速度测量从盖亚DR 2和地面观测跟踪625颗恒星的轨迹在斯科-岑OB协会从5百万年的过去到2百万年的未来。我们确定了119颗在希尔半径内至少发生过一次飞越事件的恒星，其中23颗在希尔半径0.5内经历过飞越。我们发现没有证据表明飞越事件和红外过量探测之间存在显着的相关性，虽然样品是不均匀的红外过量发射敏感。有十颗恒星过去的飞越事件主机解决拱盘出现相对对称的现有数据，除了围绕HD 106906的拱双星盘。我们确定了这些飞越事件的轨迹和相对速度，并将其与空间分辨磁盘的几何形状进行了比较。未来的工作需要测量低质量恒星的运动学，并提高整个样本对星周盘的灵敏度。
英文摘要：
High-contrast imaging studies of debris disks have revealed a significant diversity in their morphologies, including large-scale asymmetries. Theories involving stellar flybys, an external source of gravitational disturbance, have offered a plausible explanation for the origin of these morphological variations. Our study is an experiment to gain empirical evidence that has been lacking from such theories. We explore this paradigm by using astrometric and radial velocity measurements from the Gaia DR2 and ground-based observations to trace the trajectories of 625 stars in the Sco-Cen OB Association from 5 Myr in the past to 2 Myr in the future. We identified 119 stars that had at least one past flyby event occurring within one Hill radius, and 23 of these experienced flybys within 0.5 Hill radius. We found no evidence of a significant correlation between the presence of flyby events and infrared excess detections, although the sample is not uniformly sensitive to infrared excess emission. Ten stars that had past flyby events host resolved circumstellar disks that appear relatively symmetric in the existing data except for the circumbinary disk surrounding HD 106906. We determined the trajectory and relative velocity of each of these flyby events, and compared these to the geometry of the spatially-resolved disks. Future work is needed to measure the kinematics of lower mass stars and to improve sensitivity to circumstellar disks for the entire sample.
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