Disrupted asteroid P/2016 G1. II. Follow-up observations from the Hubble Space Telescope

TL;DR

Follow-up Hubble observations of asteroid P/2016 G1 confirmed a short-duration dust ejection event about 350 days before perihelion, with no detected fragments larger than 30 meters, refining previous models and mass estimates.

Contribution

This study provides the first HST follow-up confirming the dust ejection timeline and mass, and sets tighter limits on fragment sizes compared to earlier ground-based observations.

Findings

Dust ejection occurred about 350 days before perihelion.

No fragments larger than approximately 30 meters were detected.

The total dust mass ejected was estimated at around 2×10^7 kg.

Abstract

After the early observations of the disrupted asteroid P/2016 G1 with the 10.4m Gran Telescopio Canarias (GTC), and the modeling of the dust ejecta, we have performed a follow-up observational campaign of this object using the Hubble Space Telescope (HST) during two epochs (June 28 and July 11, 2016). The analysis of these HST images with the same model inputs obtained from the GTC images revealed a good consistency with the predicted evolution from the GTC images, so that the model is applicable to the whole observational period from late April to early July 2016. This result confirms that the resulting dust ejecta was caused by a relatively short-duration event with onset about 350 days before perihelion, and spanning about 30 days (HWHM). For a size distribution of particles with a geometric albedo of 0.15, having radii limits of 1 $\mu$m and 1 cm, and following a power-law with index --3.0, the total dust mass ejected is $\sim$2$\times$10$^7$ kg. As was the case with the GTC observations, no condensations in the images that could be attributed to a nucleus or fragments released after the disruption event were found. However, the higher limiting magnitude reachable with the HST images in comparison with those from GTC allowed us to impose a more stringent upper limit to the observed fragments of $\sim$30 m.