Search for the Return of Activity in Active Asteroid 176P/LINEAR

TL;DR

This study searched for activity in asteroid 176P/LINEAR during 2011 perihelion using deep optical imaging, finding no signs of activity and suggesting possible surface or subsurface changes that suppressed activity.

Contribution

The paper provides the first detailed observational analysis of 176P/LINEAR during 2011 perihelion, confirming the absence of activity and proposing explanations for the variability in activity levels.

Findings

No visible signs of activity in 2011 images

No brightness enhancements or dust emission detected

Activity observed in 2005 was not present in 2011

Abstract

We present the results of a search for the reactivation of active asteroid 176P/LINEAR during its 2011 perihelion passage using deep optical observations obtained before, during, and after that perihelion passage. Deep composite images of 176P constructed from data obtained between June 2011 and December 2011 show no visible signs of activity, while photometric measurements of the object during this period also show no significant brightness enhancements similar to that observed for 176P between November 2005 and December 2005 when it was previously observed to be active. An azimuthal search for dust emission likewise reveals no evidence for directed emission (i.e., a tail, as was previously observed for 176P), while a one-dimensional surface brightness profile analysis shows no indication of a spherically symmetric coma at any time in 2011. We conclude that 176P did not in fact exhibit activity in 2011, at least not on the level on which it exhibited activity in 2005, and suggest that this could be due to the devolatization or mantling of the active site responsible for its activity in 2005.