A short-duration event as the cause of dust ejection from Main-Belt Comet P/2012 F5 (Gibbs)

TL;DR

This study models a brief, impulsive dust ejection event from Main-Belt Comet P/2012 F5 (Gibbs), suggesting an impact rather than sublimation as the cause, with detailed analysis of dust velocities, size distribution, and nucleus size.

Contribution

It provides the first detailed interpretative model of a short-duration dust ejection event from a main-belt comet, indicating impact as the likely cause.

Findings

Dust trail resulted from an impulsive event around July 1, 2011.

Ejection velocities were 8-10 cm/s for particles 30 cm to 130 μm.

Particles follow a power-law size distribution with index ≈ -3.7.

Abstract

We present observations and an interpretative model of the dust environment of Main-Belt Comet P/2010 F5 (Gibbs). The narrow dust trails observed can be interpreted unequivocally as an impulsive event that took place around 2011 July 1st with an uncertainty of $\pm$10 days, and a duration of less than a day, possibly of the order of a few hours. The best Monte Carlo dust model fits to the observed trail brightness imply ejection velocities in the range 8-10 cm s$^{-1}$ for particle sizes between 30 cm and 130 $\mu$m. This weak dependence of velocity on size contrasts with that expected from ice sublimation, and agrees with that found recently for (596) Scheila, a likely impacted asteroid. The particles seen in the trail are found to follow a power-law size distribution of index $\approx$-3.7. Assuming that the slowest particles were ejected at the escape velocity of the nucleus, its size is constrained to about 200-300 m in diameter. The total ejected dust mass is $\gtrsim 5\times 10^8$ kg, with represents approximately 4 to 20% of the nucleus mass.