New Active Asteroid (6478) Gault

Abstract

Main-belt asteroid (6478) Gault was observed to show cometary features in early 2019. To investigate the cause, we conducted {\it BVR} observations at Xingming Observatory, China, from 2019 January to April. The two tails were formed around 2018 October 26--November 08, and 2018 December 29--2019 January 08, respectively, and consisted of dust grains of $\gtrsim$20 $\mu$m to 3 mm in radius ejected at a speed of $0.15\pm 0.05$ m s${}^{-1}$ and following a broken power-law size distribution bending at grain radius $\sim$70 $\mu$m (bulk density 1 g cm${}^{-3}$ assumed). The total mass of dust within a $10^4$ km-radius aperture around Gault declined from $\sim$$9\times 10^6$ kg since 2019 January at a rate of $2.28\pm 0.07$ kg s${}^{-1}$, but temporarily surged around 2019 March 25, because Earth thence crossed the orbital plane of Gault, within which the ejected dust was mainly distributed. No statistically significant colour or short-term lightcurve variation was seen. Nonetheless we argue that Gault is currently subjected to rotational instability. Using the available astrometry, we did not detect any nongravitational acceleration in the orbital motion of Gault.

6 pages, 4 figures, 2 tables

References in corpus (9)

• Star catalog position and proper motion corrections in asteroid astrometry
• Resurrection of (3200) Phaethon in 2016
• The Sporadic Activity of (6478) Gault: A YORP-driven event?
• Episodically Active Asteroid 6478 Gault
• Fast Rotation and Trailing Fragments of the Active Asteroid P/2012 F5 (Gibbs)
• Non-Gravitational Acceleration of the Active Asteroids
• Multiple Outbursts of Asteroid (6478) Gault
• Outbursting Comet P/2010 V1 (Ikeya-Murakami): A Miniature Comet Holmes
• Dust Properties of Double-Tailed Active Asteroid (6478) Gault

Cited by in corpus (1)

• The Pinpoint Comets: 133P/Elst-Pizarro, 249P/LINEAR, 331P/Gibbs, 62412 and 6478 Gault