KM3-230213A: An Ultra-High Energy Neutrino from a Year-Long Astrophysical Transient

Feb 18, 2025
6 pages
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Abstract: (arXiv)
The Km3NET collaboration has recently reported the detection of a neutrino event with energy in excess of 100 PeV. This detection is in 2.5-3σ\sigma tension with the upper limit on the neutrino flux at this energy imposed by IceCube and the Pierre Auger Observatory, if the event is considered part of the diffuse all-sky neutrino flux. We explore an alternative possibility that the event originates from a flare of an isolated source. We show that the data of Km3NET, IceCube and the Pierre Auger Observatory are consistent with the possibility of a source flare of duration T2T \lesssim 2 yr with muon neutrino flux F \approx 3\times 10^{-10}(1\mbox{ yr }/ T) erg cm2^{-2} s1^{-1}. Constraints on the neutrino spectrum indicate that the protons responsible for the neutrino emission have a very hard spectrum in the Ep1019E_p\gtrsim 10^{19} eV energy range, or otherwise that the neutrinos are produced by photohadronic interactions with infrared photons. The all-sky rate of similar neutrino flaring sources is constrained to be R0.4/R\lesssim 0.4/ yr.
Note:
  • 6 pages, 1 figure, prepared for submission to PRD