Three Fast-spinning Medium-sized Hilda Asteroids Uncovered by TESS

Nóra Takács, Csaba Kiss, Róbert Szakáts, Emese Plachy, Csilla E. Kalup, Gyula M. Szabó, László Molnár, Krisztián Sárneczky, Róbert Szabó, Attila Bódi and András Pál
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Abstract

Hilda asteroids, which orbit in a 3:2 resonance with Jupiter, serve as key indicators of dynamical processes in the early solar system. Their spin rates, an important probe of these mechanisms, can constrain their density and collisional evolution, offering valuable insights into their origin. In this Letter, we report on the identification of three fast-rotating Hilda asteroids with spin periods in the 3.2–3.7 hr range using data from the Transiting Exoplanet Survey Satellite. These rotation periods are significantly shorter than the previous ∼5.0 hr shortest rotation periods obtained from ground-based observations in the ∼10 km size range and are comparable with the ∼3.0 hr breakup limit of Hildas a few kilometers in size, derived from the FOSSIL survey. These fast-rotating asteroids require either considerable cohesion (in the order of a few kPa) or densities ρ ≳1.5 g cm−3, in contrast to the typically assumed ρ ≲1 g cm−3, to prevent rotational breakup. C-type asteroids, which are common in the outer main belt, have densities of ρ ≈ 1.5 g cm−3 and are known to comprise a small but notable fraction of Hildas. The observed occurrence rate of the ≤4 hr rotation periods may be explained by the 10%–15% fraction of C-type asteroids, likely mixed into these populations from the outer main belt during giant planet dynamical interactions in the early solar system.
TESS发现了三颗快速旋转的中型希尔达小行星
希尔达小行星与木星以3:2的共振轨道运行,是早期太阳系动力学过程的关键指标。它们的自旋速率是对这些机制的重要探测,可以限制它们的密度和碰撞演化,为它们的起源提供有价值的见解。在这封信中,我们报告了利用凌日系外行星测量卫星的数据识别出三颗旋转周期在3.2-3.7小时范围内的快速旋转的希尔达小行星。这些旋转周期明显短于以前在~ 10公里大小范围内从地面观测获得的~ 5.0小时的最短旋转周期,并且与化石调查得出的几公里大小的Hildas的~ 3.0小时分裂极限相当。这些快速旋转的小行星要么需要相当大的内聚力(以几kPa的数量级),要么需要ρ > 1.5 g cm−3的密度,而不是通常假设的ρ > 1 g cm−3,以防止旋转破裂。c型小行星常见于外主带,密度为ρ≈1.5 g cm−3,已知在希尔达斯中占很小但值得注意的比例。观测到的≤4小时旋转周期的发生率可以用10%-15%的c型小行星来解释,这些小行星可能是在太阳系早期巨行星动力学相互作用期间从外主带混合到这些小行星群中的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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