NEOWISE Observations of Distant Active Long-period Comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini)

Abstract

Hyperactive comet activity typically becomes evident beyond the frost line (∼3–4 au) where it becomes too cold for water-ice to sublimate. If carbon monoxide (CO) and carbon dioxide (CO _2 ) are the species that drive activity at sufficiently large distances, then detailed studies on the production rates of these species are extremely valuable to examine the formation of the solar system because these two species (beyond water) are next culpable for driving cometary activity. The NEOWISE reactivated mission operates at two imaging bandpasses, W 1 and W 2 at 3.4 μ m and 4.6 μ m, respectively, with the W 2 channel being fully capable of detecting CO and CO _2 at 4.67 μ m and 4.23 μ m in the same bandpass. It is extremely difficult to study CO _2 from the ground due to contamination in Earth’s atmosphere. We present our W 1 and W 2 photometry, dust measurements, and findings for comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini), hereafter, B1, K2, and U3, respectively. Our results assess CO and CO _2 gas production rates observed by NEOWISE. We have determined: (1) comets B1 and K2 have CO _2 and CO gas production rates of ∼10 ^27 and ∼10 ^29 molecules s ^−1 , respectively, if one assumes the excess emission is attributed to either all CO or all CO _2; (2) B1 and K2 are considered hyperactive in that their measured Af ρ dust production values are on the order of ≳10 ^3 cm; and (3) the CO and CO _2 production rates do not always follow the expected convention of increasing with decreased heliocentric distance, while B1 and K2 exhibit noticeable dust activity on their inbound leg orbits.

Keywords

• Long period comets
• Infrared astronomy
• Photometry
• Astronomy data analysis
• Comet volatiles