SN 2023gfo: A peculiar type IIP supernova with high luminosity and normal plateau duration

Abstract

We present near-infrared (NIR) and optical observations of the highly reddened Type IIP supernova (SN) 2023gfo in the nearby galaxy NGC 4995 (d = 26.4 ± 3.2 Mpc), which reached a high peak luminosity of MV = -18.6 mag. The SN was initially detected as a faint red event, with B - V = 0.8 mag at the beginning of the plateau phase. By comparison with the template, we estimate a total extinction of AV = 2.1 mag. After correcting for this extinction, we derive a peak quasi-bolometric luminosity of (5.9 ± 1.5) × 1042 erg s-1, placing this event among the most luminous SNe IIP, while its plateau duration remains within the normal range. The early-phase optical spectrum exhibits a P-Cygni profile of Hα, with a broad absorption of V = 13,800 km s-1, which is among the highest observed for SNe IIP at comparable epochs. The high luminosity and the normal plateau duration suggest that this event represents an outlier. Applying an analytical model, we infer an unusually large progenitor radius. This may indicate that the progenitor experienced an extreme energy injection from the core to the envelope shortly before explosion, resulting in a substantially inflated radius. While ejecta--circumstellar matter (CSM) interaction could in principle account for the high luminosity, we find no observational evidence supporting strong interaction.