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 August and November 2018, and January 2019. 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 ob- served 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 Afρ 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 arcsec), indicating a range from moderate to high activity levels. Dust mass loss rates were estimated from 328.1 kg/s for comet 64P/Swift-Gehrels to 1395.5 kg/s for comet C/2017 M4 (ATLAS). The color indices of comets 38P/Stephan-Oterma and C/2017 M4 (ATLAS) closely resemble the average col- ors of active short-period comets (SPCs) and active long-period comets (LPCs), respectively. In contrast, 64P/Swift-Gehrels exhibit a significantly bluer hue than typical Jupiter Family Comets (JFCs).