Program: GN-2024B-Q-209

While core-collapse supernovae (CCSNe) often show early and consistent signs of circumstellar (CSM) interaction, some exhibit delayed signatures due to interaction with material far from the progenitor. The presence of dense circumstellar material is a powerful probe of terminal mass loss in massive stars, that have widespread implications for astrophysics. Traditionally, delayed CSM interaction is inferred from spectroscopic signatures in deep late-time spectroscopy, faint late-time optical plateaus or radio/X-ray indicators, each being prohibitively expensive for large searches. The mid-infrared (MIR) bands tracing the warm dust around CCSNe offer a powerful probe of dust formation or dust heating induced by CSM interaction, but have been historically very limited. We have recently used the largest flux-limited SN catalog from the Zwicky Transient Facility together with a new image subtraction pipeline for the synoptic NEOWISE MIR survey to search for MIR emission from CCSNe. We identify a complete sample of seven CCSNe exhibiting late MIR brightening episodes strongly indicative of delayed CSM interaction that are not detected at optical wavelengths. Motivated by spectroscopic confirmation in one pilot event, we request 13 hours of GMOS spectroscopy of the sample to open a new window into terminal mass loss using synoptic IR observations.