Photometric properties of comet C/2021 S3 (PANSTARRS) based on observations in 2024

We present the results of CCD photometric observations of comet C/2021 S3 (PANSTARRS), carried out during its post-perihelion period at the Sanglokh International Astronomical Observatory of the Institute of Astrophysics, National Academy of Sciences of Tajikistan (MPC code 193). The observations were conducted over five nights in June–July 2024 using the Zeiss-1000 telescope equipped with CCD camera FLI ProLine 16803 and broadband UBVR and I filters of the Johnson–Cousins photometric system. Image reduction and photometric measurements were performed following standard procedures, utilizing the Tycho Tracker software and the ATLAS star catalog. The photometric aperture was selected based on optimization of the signal-to-noise ratio. The measured apparent and absolute magnitudes reveal an increase in the comet’s brightness of approximately one magnitude from June to July, which is likely associated with a localized dust outburst. This interpretation is supported by the observed coma morphology and estimates of the dust production parameter. During the observational period, the comet was located at a heliocentric distance of 2.2–2.7 AU and continued to exhibit activity driven by solar heating.