Two 100 TeV Neutrinos Coincident with the Seyfert Galaxy NGC 7469

Abstract In 2013, the IceCube collaboration announced the detection of a diffuse high-energy astrophysical neutrino flux. The origin of this flux is still largely unknown. The most significant individual source is the close-by Seyfert galaxy NGC 1068 at the 4.2σ level with a soft spectral index. To identify sources based on their counterpart, IceCube releases real-time alerts corresponding to neutrinos with a high probability of astrophysical origin. We report here the spatial coincidence of two neutrino alerts, IC 220424A and IC 230416A, with the Seyfert galaxy NGC 7469 at a distance of 70 Mpc. We evaluate, a posteriori, the chance probability of such a coincidence and discuss this source as a potential neutrino emitter based on its multiwavelength properties and in comparison to NGC 1068 by performing a goodness-of-fit test. A test statistic is derived from a likelihood ratio that includes the neutrino angular uncertainty and the source distance. We apply this test first to a catalog of active galactic nucleus sources and second to a catalog of Seyfert galaxies only. Our a posteriori evaluation excludes the possibility of an accidental spatial coincidence of both neutrinos with the Seyfert galaxy NGC 7469 at the 3.2σ level, leaving open the possibility that either one or both neutrinos originated from the source. To be compatible with nondetections of TeV neutrinos, the source would need to have a hard spectral index.