IceCube-HAWC coincidences

Let’s use the event NuEm-240118A to introduce a category of special multi-messenger events: sub-threshold coincidences discovered by the AMON network. The Astrophysical Multimessenger Observatory Network (AMON) is a unique infrastructure that performs real-time correlations of (sub-threshold) signals across all known astronomical messengers – photons, neutrinos, cosmic rays, and gravitational waves. Sub-threshold in this context means that the individual signals of each participating detector are not showing a significant excess above the typical noise levels. The hope is, that by detecting spatial and temporal coincidences across multiple, independent instruments, a possibly interesting transient phenomena can be found.

The event NuEm-240118A is the result of such a search: AMON is here combining high-energy neutrinos detected by the IceCube observatory with data from the HAWC array detecting high-energy gamma rays. The combined data is still not terribly significant: similar events are found as chance coincidences of noise fluctuations roughly twice a year. Nevertheless, additional observations of the region defined by the AMON alert could provide crucial additional information. Unfortunately it is already clear from a cone search in Astro-COLIBRI, that there is no known, Fermi-LAT high-energy gamma-ray source in this region of the sky. Maybe searches in other catalogs will find something?

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