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 350(+30)(-10) days before perihelion (i.e., around 2016 February 10), starting sharply and decreasing with 24(-7)(+10) days (HWHM). The results of the modeling imply that the emission of similar to 1.7. x. 10(7) kg of dust, if composed of particles of 1 mu m 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 similar to 50 m in radius is derived.This work was supported by contracts AYA2015-67152-R and AYA2015-71975-REDT from the Spanish Ministerio de Economia y Competitividad. J.L. gratefully acknowledges support from contract AYA2015-67772-R.Peer reviewe