New observational evidence of active asteroid P/2010 A2: Slow rotation of the largest fragment

Abstract

We report new observations of the active asteroid P/2010 A2 taken when it made its closest approach to the Earth (1.06 au in 2017 January) after its first discovery in 2010. Despite a crucial role of the rotational period in clarifying its ejection mechanism, the rotational property of P/2010 A2 has not yet been studied due to the extreme faintness of this tiny object ($\sim$120 m in diameter). Taking advantage of the best observing geometry since the discovery, we succeed in obtaining the rotational light curve of the largest fragment with Gemini/GMOS-N. We find that (1) the largest fragment has a double-peaked period of $11.36\pm 0.02$ hr spinning much slower than its critical spin period; (2) the largest fragment is a highly elongated object ($a/b⩾1.94$) with an effective radius of $61.9_{-9.2}^{+16.8}$ m; (3) the size distribution of the ejecta follows a broken power law (the power indices of the cumulative size distributions of the dust and fragments are $2.5\pm 0.1$ and $5.2\pm 0.1$, respectively); (4) the mass ratio of the largest fragment to the total ejecta is around 0.8; and (5) the dust cloud morphology is in agreement with the anisotropic ejection model in Kim et al. (2017). These new characteristics of the ejecta obtained in this work are favorable to the impact shattering hypothesis.

accepted by ApJL

References in corpus (6)

• K-corrections and filter transformations in the ultraviolet, optical, and near infrared
• A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2
• The shape distribution of asteroid families -- evidence for evolution driven by small impacts
• Fast Rotation and Trailing Fragments of the Active Asteroid P/2012 F5 (Gibbs)
• Fragmentation Kinematics in Comet 332P/Ikeya-Murakami
• Discovery and Characteristics of the Rapidly Rotating Active Asteroid (62412) 2000 SY178 in the Main Belt

Cited by in corpus (3)

• Episodically Active Asteroid 6478 Gault
• Activity of main-belt comet 324P/La Sagra
• Broadband photometry of asteroid 6478 Gault: activity and morphology