No Activity Among 13 Centaurs Discovered in the Pan-STARRS1 Detection Database

TL;DR

This study observed 13 Centaurs from the Pan-STARRS1 database, finding no activity and setting upper limits on volatile and dust production, suggesting most are dormant or inactive despite orbital evolution that could trigger activity.

Contribution

It provides the first comprehensive observational and thermo-dynamical analysis of these 13 Centaurs, highlighting their inactivity and potential for future activity based on orbital history.

Findings

No activity detected in any of the 13 Centaurs.

Upper limits on volatile and dust production are significantly lower than active comets.

One Centaur shows signs of potential future outburst due to orbital changes.

Abstract

Centaurs are small bodies orbiting in the giant planet region which were scattered inwards from their source populations beyond Neptune. Some members of the population display comet-like activity during their transition through the solar system, the source of which is not well understood. The range of heliocentric distances where the active Centaurs have been observed, and their median lifetime in the region suggest this activity is neither driven by water-ice sublimation, nor entirely by super-volatiles. Here we present an observational and thermo-dynamical study of 13 Centaurs discovered in the Pan-STARRS1 detection database aimed at identifying and characterizing active objects beyond the orbit of Jupiter. We find no evidence of activity associated with any of our targets at the time of their observations with the Gemini North telescope in 2017 and 2018, or in archival data from 2013 to 2019. Upper limits on the possible volatile and dust production rates from our targets are 1-2 orders of magnitude lower than production rates in some known comets, and are in agreement with values measured for other inactive Centaurs. Our numerical integrations show that the orbits of six of our targets evolved interior to r$\sim$15 AU over the past 100,000 years where several possible processes could trigger sublimation and outgassing, but their apparent inactivity indicates their dust production is either below our detection limit or that the objects are dormant. Only one Centaur in our sample -- 2014 PQ$_{70}$ experienced a sudden decrease in semi-major axis and perihelion distance attributed to the onset of activity for some previously known inactive Centaurs, and therefore is a likely candidate for future outburst. This object should be a target of interest for further observational monitoring.