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

Abstract

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 $1.3_{-0.4}^{+0.7}\times 10^{43}$ erg s${}^{-1}$ before fading away with a light-curve drop at $\sim 300$ days. We present late-time HST/WFC3 ultraviolet (UV) imaging and Keck/LRIS spectroscopy at $\sim 1200$ 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$\alpha$ 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 $\sim 2.7M_{\odot }$ of nearby, dense CSM within a radius of $\sim 10^{16}$ cm surrounded by wind-like outer CSM with a mass-loss rate of $\sim 10^{-4}{{\mathrm{M}}_{\odot }\mathrm{yr}}^{-1}$. The broken density profile indicates $\gtrsim 100\times$ 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.

15 pages, 5 figures, 2 tables. Submitted to ApJ