EARLY EVOLUTION of DISRUPTED ASTEROID P/2016 G1 (PANSTARRS)

We present deep imaging observations of activated asteroid P/2016 G1 (PANSTARRS) using the 10.4 m Gran Telescopio Canarias (GTC) from 2016 late April to early June. The images are best interpreted as the result of a relatively short-duration event with an onset of about days before perihelion (i.e., around 2016 February 10), starting sharply and decreasing with days (HWHM). The results of the modeling imply that the emission of ∼1.7 107 kg of dust, if composed of particles of 1 μm to 1 cm in radius, is distributed following a power law of index -3 and having a geometric albedo of 0.15. A detailed fitting of a conspicuous westward feature in the head of the comet-like object indicates that a significant fraction of the dust was ejected along a privileged direction right at the beginning of the event, which suggests that the parent body has possibly suffered an impact followed by a partial or total disruption. From the limiting magnitude reachable with the instrumental setup, and assuming a geometric albedo of 0.15 for the parent body, an upper limit for the size of possible fragment debris of ∼50 m in radius is derived.