Activity in Jupiter-family comets and asteroids: photometric analysis of survey and deep imaging

Abstract

Jupiter-family comets (JFCs) exhibit a wide range of activity levels and mass loss over their orbits. Using 34,046 images, we analysed 116 active JFCs with ATLAS, focusing on those reaching perihelion from 2020–2023. Dust production rates were measured via Afρ, showing most JFCs peak in activity after perihelion, typically within 2.5 au of the Sun, likely driven by water-ice sublimation. We measured the activity indices of 56 JFCs and found that on average, the rate of change of activity post-perihelion was shallower than pre-perihelion. We also identified five JFC nuclei with no visible coma, estimating upper limits for their radii, consistent with previous studies. Additionally, eleven outbursts were detected, with magnitude increases ranging from +0.2 to +2.8, matching typical JFC behaviour. Exploring the evolution of short-period comets, we observed 16 asteroids and 7 comets for low-level activity using the Isaac Newton Telescope. Surface brightness profiles indicated activity in three asteroids, suggesting reclassification as weakly sublimating cometary nuclei. These findings imply that up to 33% of objects in the 3.16–4.56 au range might exhibit low-level activity. We used aperture photometry techniques to measure the r-band magnitudes for each asteroid and comet we observed. The brightest target we observed was 6144 Kondojiro (1994 EQ3) at 19.41 ± 0.03 mag and the faintest target was 2020 RX133 at 22.07 ± 0.09 mag. We found that the median (g-r) colour index and standard deviation for our asteroid sample was (g-r) = 0.52 ± 0.13 which indicated that most of our colours aligned with those expected for D-type asteroids within 1σ. Notably three asteroids, 371548 (2006 UY349), 2011 WM183 and 2015 MW21, exhibited significantly lower (g-r) values.

Date of Award	Jul 2025
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Alan Fitzsimmons (Supervisor) & Megan Schwamb (Supervisor)