Program: GN-2024B-Q-114

We request Gemini observing time to obtain monitoring observations using GMOS-N and GMOS-S to study the activity evolution of main-belt comets (MBCs) 133P and 457P, both of which are expected to be active in 2024B and are targets of approved JWST Cycle 3 observations. JWST recently detected water outgassing in a MBC for the first time in Cycle 1 (which had not been possible before then from existing facilities), and will observe three more MBCs in Cycles 2 and 3, visiting one of those MBCs twice. Contemporaneous JWST and ground-based observations of MBCs enable researchers to determine typical ratios of water production rates measured from space to dust production rates measured from the ground, and then use that information to estimate water production rates from the much larger set of available ground-based observations of MBCs. Our proposed observations will maximize the science return from the planned JWST observations, help to extend the impact of limited JWST data to a much larger population of objects than would be possible to study with JWST alone, and will also contribute to efforts to characterize long-term MBC activity evolution.