SN2023syz and SN2025cbj: 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. IC231027A and IC250421A coincide with the positions of SN2023syz and SN2025cbj, 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 such two coincidences occurring by chance in our sample is $p \sim 0.67\%$, 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 IC231027A is low, implying that the association between IC231027A and SN2023syz is likely coincidental. Nevertheless, under optimistic parameters, the probability of detecting a neutrino from the whole SNe IIn sample could reach $\gtrsim6\%$, 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.

Figures (8)

• Figure 1: Sky distributions in equatorial coordinates of the SNe IIn and alert events adopted in this work. The black points represent the positions of 163 SNe IIn, and the red points represent the locations of 138 alert events.
• Figure 2: Neutrino event rates integrated over different energy ranges as a function of the time after the shock breakout for SN2023syz and SN2025cbj, respectively. The results assume the following parameters sets: $(E_k, R_{\rm CSM}) = (8\times10^{50} \rm erg, 4\times10^{16} cm)$ for SN2023syz and $(E_k, R_{\rm CSM}) = (3\times10^{52} \rm erg, 4\times10^{16} cm)$ for SN2025cbj, respectively. The blue band denotes the variation arising from varying the $M_{\rm ej}$ and $M_{\rm CSM}$ parameters in the range of ($M_{\rm ej}$, $M_{\rm CSM}$) $\in$ ($[1 - 20]\,M_{\odot}$, $[1 - 30]\,M_{\odot}$) for SN2023syz and ($M_{\rm ej}$, $M_{\rm CSM}$) $\in$ ($[1 - 70]\,M_{\odot}$, $[1 - 70]\,M_{\odot}$) for SN2025cbj. When deriving the blue band, we have excluded the parameters not satisfying $t_{\rm rise}\leq t_{\rm rise,obs} \leq1.5 t_{\rm rise}$ and $t_{\rm CSM}-t_{\rm bo}$ greater than the observed time delay, please see the main text and Figure \ref{['fig: total events']} for details.
• Figure 3: Expected total number of neutrinos, integrated over different energy ranges, from SN 2023syz (upper panels) and SN 2025cbj (lower panels). We scan the parameters of ($M_{\rm ej}$, $M_{\rm CSM}$) = ($[1 - 20]\,M_{\odot}$, $[1 - 20]\,M_{\odot}$); ($M_{\rm ej}$, $M_{\rm CSM}$) = ($[1 - 70]\,M_{\odot}$, $[1 - 70]\,M_{\odot}$) to show how the expected number relies on these parameters for SN2023syz and SN2025cbj, respectively. The gray shaded region in the figure represents the excluded parameters for which the expected $t_{\rm rise}$ and $t_{\rm {CSM}} - t_{\rm{bo}}$ do not match the observations.
• Figure 4: A comparison of the RA and DEC distributions between the real SN IIn catalog and one realization of the mock catalogs.
• Figure 5: This figure is the Fermi-LAT counts map in the 100 MeV - 1 TeV energy range, showing the integrated search in the period of $\pm$ 120 days of the arrival date of IC231027A. The position of IC231027A is marked by the red 'X' with the 90% positional uncertainty denoting by the red circle (only statistical error). The orange star is the position of SN2023syz. The white circle and plus sign are the positions of two 4FGL sources within the error circle of IC231027A (i.e. 4FGL J1749.6+4716 and 4FGL J1747.9+4704), away from the best fit position of IC231027A 0.16 deg and 0.29 deg, respectively.