Multi-Wavelength Identification of a Luminous Mid-Infrared Supernova Powered by Circumstellar Interaction with Binary-Driven Pre-supernova Mass Loss

Terminal mass-loss in massive stars is commonly reconstructed from observations of circumstellar interaction in core-collapse supernovae (CCSNe); however, such signatures can be easily missed depending on the phase when they appear. In this paper, we present a multi-wavelength study of SN,2022yyz, a nearby CCSN selected by its luminous late-time mid-infrared (MIR) excess in NEOWISE at > 500 days after the discovery. Classified as a Type II SN at discovery, it reached a peak bolometric luminosity of 1.3+0.7-0.4 times10 43 erg s-1 before fading away with a light-curve drop at about 300 days. We present late-time HST/WFC3 ultraviolet (UV) imaging and Keck/LRIS spectroscopy at about 1200 days, which reveal clear signs of circumstellar-medium (CSM) interaction via a UV excess consistent with a strong MgII contribution and a flat-topped H α profile. We show that the bolometric light curve and the late-time UV luminosity can be explained using a semi-analytic CSM interaction model involving a broken power-law density profile: with about 2.7 M of nearby, dense CSM within a radius of about 10 16 cm surrounded by wind-like outer CSM with a mass-loss rate of about 10-4 M yr-1. The broken density profile indicates 100 times mass-loss rate enhancement starting a few hundred years before explosion, pointing to a possible common-envelope ejection in a binary system. Despite being overlooked for follow-up at such proximity, our results demonstrate that IR photometric selection methods provide a powerful way of mapping terminal mass-loss in massive stars - laying the groundwork for the Roman Space Telescope surveys.