Understanding the activity performance of comets 38P/Stephan-Oterma, 64P/Swift-Gehrels and C/2017 M4 (ATLAS) through broadband photometric observations

In this work, we report observations of three comets: 38P/Stephan-Oterma, 64P/Swift-Gehrels, and C/2017 M4 (ATLAS), conducted with the Nanshan one-meter wide-field telescope in 2018 August and November, and 2019 January. We extracted morphological features through image enhancement techniques and calculated the dust activity parameter, Afρ , along with dust mass loss rates and coma color indices using broadband photometric data. Our morphological analysis uncovered a spectrum of dust characteristics among the observed comets, ranging from a significant twisted structure in comet 38P/Stephan-Oterma’s coma to the regular coma envelope surrounding comet 64P/Swift-Gehrels. The Af ρ values varied between 148.8 ± 0.3 cm for 64P/Swift-Gehrels and 1118.5 ± 6.2 cm for C/2017 M4 (ATLAS) (measured within a reference aperture radius of ρ = 6″), indicating a range from moderate to high activity levels. Dust mass loss rates were estimated from 328.1 kg s −1 for comet 64P/Swift-Gehrels to 1395.5 kg s −1 for comet C/2017 M4 (ATLAS). The color indices of comets 38P/Stephan-Oterma and C/2017 M4 (ATLAS) closely resemble the average colors of active short-period comets and active long-period comets, respectively. In contrast, 64P/Swift-Gehrels exhibits a significantly bluer hue than typical Jupiter family comets.