WISE/NEOWISE observations of Active Bodies in the Main Belt

TL;DR

This study uses WISE mid-infrared data to analyze the physical properties and activity levels of active main belt objects, providing new insights into their composition, dust environment, and activity status.

Contribution

It presents the first mid-infrared measurements of several AMBOs, constrains their sizes, albedos, and dust particle distributions, and compares activity levels with other known comets.

Findings

Most AMBOs have low albedos similar to comet nuclei.

Dust particle size distribution is shallower than typical comets.

Upper limits on CO2 and CO production were established.

Abstract

We report results based on mid-infrared photometry of 5 active main belt objects (AMBOs) detected by the Wide-field Infrared Survey Explorer (WISE) spacecraft. Four of these bodies, P/2010 R2 (La Sagra), 133P/Elst-Pizarro, (596) Scheila, and 176P/LINEAR, showed no signs of activity at the time of the observations, allowing the WISE detections to place firm constraints on their diameters and albedos. Geometric albedos were in the range of a few percent, and on the order of other measured comet nuclei. P/2010 A2 was observed on April 2-3, 2010, three months after its peak activity. Photometry of the coma at 12 and 22 {\mu}m combined with ground-based visible-wavelength measurements provides constraints on the dust particle mass distribution (PMD), dlogn/dlogm, yielding power-law slope values of {\alpha} = -0.5 +/- 0.1. This PMD is considerably more shallow than that found for other comets, in particular inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. It is similar to the PMD seen for 9P/Tempel 1 in the immediate aftermath of the Deep Impact experiment. Upper limits for CO2 & CO production are also provided for each AMBO and compared with revised production numbers for WISE observations of 103P/Hartley 2.