High-energy neutrino emission from the Seyfert galaxy NGC 7469

Abstract In the recent years we are witnessing the birth of high-energy neutrino astronomy. In 2013, the IceCube collaboration announced the detection of a high-energy astrophysical neutrino flux and in 2022 the highest evidence to date (4.2 sigma) of neutrino emission from a single source, the Seyfert galaxy NGC 1068. Nevertheless, as the great majority of sources is still unidentified, IceCube sends out realtime alerts for neutrinos with a high probability of astrophysical origin to encourage electromagnetic follow-up with the goal to identify new counterparts. The two neutrino alerts IC220424A and IC230416A, with energies around 100 TeV, both coincided with the Seyfert galaxy NGC 7469, 70 Mpc away. To determine whether this coincidence happened by chance, we designed a statistical test to determine the p-value of the background hypothesis. As a result, we get a p-value of 4.4×10−4, disfavoring the background scenario with a significance of 3.3σ. NGC 7469 was undetected in previous IceCube point source searches. To explain the association of the two high-energy neutrinos together with the non-detection, the neutrino spectrum would have to follow a power-law with a hard spectral index. Such a neutrino spectrum would differ greatly from the soft power-law associated with NGC 1068.