SN 2023syz and SN 2025cbj: Two Type IIn Supernovae Associated with IceCube High-energy Neutrinos

Abstract Type IIn supernovae (SNe IIn) are a subclass of core-collapse SNe in which strong interactions occur between the ejecta and dense circumstellar material, creating ideal conditions for the production of high-energy neutrinos. This makes them promising candidate sources of neutrinos. In this work, we conduct an association study between 163 SNe IIn observed by the Zwicky Transient Facility and 138 neutrino alert events detected by the IceCube Neutrino Observatory. After excluding alerts with poor localization, we find two SNe that are spatiotemporally coincident with neutrino events. IC 231027A and IC 250421A coincide with the positions of SN 2023syz and SN 2025cbj, respectively, within their localization uncertainties, and the neutrino arrival times are delayed by 38 days and 61 days relative to the discovery times of the corresponding SNe. Using Monte Carlo simulations, we estimate that the probability of two such events occurring by chance in our sample is p ∼ 0.67%, suggesting that they may originate from genuine physical associations, though the result is not yet statistically significant. Our model calculations, however, indicate that the likelihood of a neutrino originating from IC 231027A is low, implying that the association between IC 231027A and SN 2023syz is likely coincidental. Nevertheless, under optimistic parameters, the probability of detecting a neutrino from the whole SNe IIn sample could reach ≳6%, indicating that detecting neutrino emission from the SNe population may be possible. Our study provides a systematic analysis, combining statistical analysis and model calculations, to assess whether interacting supernovae can serve as potential sources of neutrino emission.