Hubble Asteroid Hunter III. 新发现小行星的物理性质
Hubble Asteroid Hunter III. Physical properties of newly found asteroids
AI总结：
本文通过分析HST存档图像中632颗小行星的视差轨迹，测定其绝对星等和尺寸，发现样本以主带天体为主，并将绝对星等累积分布的斜率变化结果扩展了约两个星等。
摘要：
确定小行星的尺寸分布是理解内太阳系碰撞历史和演化的关键。我们旨在通过确定Hubble Space Telescope (HST) Archive中新发现小行星的视差，进而确定它们的绝对星等和尺寸，以增进我们对主带小行星尺寸分布的了解。由于航天器的快速轨道运动引起的视差效应，小行星在HST图像中呈现为弯曲的轨迹。通过将模拟轨迹拟合到观测到的轨迹，可以计算出视差效应，从而获得小行星的距离。利用距离，在假设反照率值的情况下，我们可以获得该天体的绝对星等和尺寸估计，以及其轨道参数的一些边界。在这项工作中，我们分析了在ESA HST Archive中发现的632颗偶然成像的小行星集合。在之前的工作中，使用了一种目标检测机器学习算法来执行此任务。我们的原始数据包含来自未知天体（与MPC数据库中的任何条目不匹配）的1,031条小行星轨迹。我们还发现了来自已知天体（在MPC中具有匹配条目的天体）的670条轨迹。经过精度评估和过滤过程，我们分析的HST数据集包含454个未知天体和178个已知天体。我们获得的样本以潜在的主带天体为主，其绝对星等（H）主要在15到22 mag之间。绝对星等累积分布证实了先前报告的15 < H < 18范围内的斜率变化，从0.56变为0.26，在我们的情况中该变化一直维持到绝对星等约为H = 20，从而将先前的结果扩展了约两个星等。由于望远镜指向在天空中的统计随机分布且覆盖了很长的时间段，HST存档观测可以用作小行星巡天。
英文摘要：
Determining the size distribution of asteroids is key for understanding the collisional history and evolution of the inner Solar System. We aim at improving our knowledge on the size distribution of small asteroids in the Main Belt by determining the parallaxes of newly detected asteroids in the Hubble Space Telescope (HST) Archive and hence their absolute magnitudes and sizes. Asteroids appear as curved trails in HST images due to the parallax induced by the fast orbital motion of the spacecraft. The parallax effect can be computed to obtain the distance to the asteroids by fitting simulated trajectories to the observed trails. Using distance, we can obtain the object's absolute magnitude and size estimation assuming an albedo value, along with some boundaries for its orbital parameters. In this work we analyse a set of 632 serendipitously imaged asteroids found in the ESA HST Archive. An object-detection machine learning algorithm was used to perform this task during previous work. Our raw data consists of 1,031 asteroids trails from unknown objects (not matching any entries in the MPC database). We also found 670 trails from known objects (objects featuring matching entries in the MPC). After an accuracy assessment and filtering process, our analysed HST set consists of 454 unknown objects and 178 known objects. We obtain a sample dominated by potential Main Belt objects featuring absolute magnitudes (H) mostly between 15 and 22 mag. The absolute magnitude cumulative distribution confirms the previously reported slope change for 15 < H < 18, from 0.56 to 0.26, maintained in our case down to absolute magnitudes around H = 20, hence expanding the previous results by approximately two magnitudes. HST archival observations can be used as an asteroid survey since the telescope pointings are statistically randomly oriented in the sky and they cover long periods of time.
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