Investigating IceCube Neutrino Alerts with the HAWC Gamma-Ray Observatory

Neutrino emission from astrophysical sources has long been considered a signature of cosmic-ray acceleration. The IceCube Neutrino Observatory has observed a diffuse flux of TeV–PeV neutrinos, but very few confirmed sources have emerged. With the recent publication of the IceCube Event Catalog (IceCat-1), IceCube has released a list of probable astrophysical neutrinos from 2011 May to 2020 December, with follow-up alerts released via the Astrophysical Multi-messenger Observatory Network (AMON). Using the archival data from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, we search for gamma-ray outbursts spatially coincident with these neutrino alerts using a Bayesian block algorithm. In this work, we consider 380 alerts, up to 2026 May 19, that are within HAWC’s field of view. We observe approximately a 5% coincident detection rate, which is consistent with expectations from background. Two of these detections contain the active galactic nuclei (AGNs) Mrk 421 and Mrk 501. We discuss the possibility of these AGNs producing the observed neutrino events when considering the HAWC results.