标题： 约2米直径的近地小行星2015 TC25的物性特征：可能来自E型小行星(44)努萨的一块巨石 显示英文标题

标题： Physical Characterization of ~2-meter Diameter Near-Earth Asteroid 2015 TC25: A possible boulder from E-type Asteroid (44) Nysa

摘要： 近地小行星（直径>20米）很有趣，因为它们是地球收集的陨石的前身。 理解我们的大气层过滤低强度撞击物的有效性，关键在于这些近地小行星的物理特性。 过去，由于在近距离飞掠地球之前难以探测到它们，对小近地天体的特征化一直是一项挑战。 在这项研究中，我们利用地面光学、近红外和雷达设备，在2015年10月一颗距离地球69,000英里的近地小行星2015 TC25飞掠地球时对其进行了物理特征分析。 我们的观测表明，其表面成分与奥伯恩陨石相似，这是一种罕见的高反照率分异型陨石。 奥伯恩陨石仅占地球陨石收集中的所有已知陨石的0.14%。 2015 TC25的自转速度也非常快，旋转周期为133秒。 我们将2015 TC25的光谱和动力学特性与其他天体进行比较，并发现内主小行星带中直径70公里的E型小行星（44）Nyssa是最有可能的来源天体。 我们认为这两个天体在光谱斜率上的差异是由于2015 TC25表面缺乏风化层。 利用E型小行星（50-60%）的反照率，我们进一步将2015 TC25的直径精炼为2米，使其成为有史以来被表征过的最小的近地小行星之一。 显示英文摘要

摘要： Small near-Earth asteroids (>20 meters) are interesting because they are progenitors for meteorites in our terrestrial collection. Crucial to our understanding of the effectiveness of our atmosphere in filtering low-strength impactors is the physical characteristics of these small near-Earth asteroids (NEAs). In the past, characterization of small NEAs has been a challenge because of the difficulty in detecting them prior to close Earth flyby. In this study we physically characterized the 2-meter diameter near-Earth asteroid 2015 TC25 using ground-based optical, near-infrared and radar assets during a close flyby of the Earth (distance 69,000 miles) in Oct. 2015. Our observations suggest that its surface composition is similar to aubrites, a rare class of high albedo differentiated meteorites. Aubrites make up only 0.14 % of all know meteorites in our terrestrial meteorite collection. 2015 TC25 is also a very fast rotator with a rotation period of 133 seconds. We compared spectral and dynamical properties of 2015 TC25 and found the best candidate source body in the inner main belt to be the 70-km diameter E-type asteroid (44) Nysa. We attribute difference in spectral slope between the two objects to the lack of regolith on the surface of 2015 TC25. Using the albedo of E-type asteroids (50-60%) we refine the diameter of 2015 TC25 to 2-meters making it one of the smallest NEA ever to be characterized.