标题： 2015 TC25近地小行星约2米直径的物理特性：来自E型小行星(44) Nysa的可能岩块 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： 小近地天体（>20米）有趣是因为它们是我们在地球收集中的陨石的母体。 理解我们大气层在过滤低强度撞击物方面的有效性至关重要，这需要了解这些小近地天体（NEAs）的物理特性。 过去，对小NEAs的表征是一个挑战，因为在接近地球飞越之前很难检测到它们。 在本研究中，我们使用地面光学、近红外和雷达资源在2015年10月地球近距离飞越（距离69,000英里）期间对直径为2米的近地天体2015 TC25进行了物理表征。 我们的观测表明，其表面成分类似于aubrites，这是一种稀有的高反照率分化的陨石。 aubrites仅占我们地球陨石收藏中所有已知陨石的0.14%。 2015 TC25也是一个非常快速的旋转体，旋转周期为133秒。 我们比较了2015 TC25的光谱和动力学特性，发现内主带中最合适的来源天体是直径70公里的E型小行星（44）Nysa。 我们将这两个物体之间的光谱斜率差异归因于2015 TC25表面缺乏风化层。 利用E型小行星的反照率（50-60%），我们将2015 TC25的直径修正为2米，使其成为被表征过的最小的NEA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.