Speaker
Description
The sources of high-energy astrophysical neutrinos remain largely unknown. Multi-wavelength observational campaigns have identified a few plausible candidates, but their numbers are very few. We look for an excess of high-energy neutrino events originating from blazar sources, compared to the number we expect from background sources. We generate random samples of events following the right ascension and declination distributions of the high-energy neutrino events detected by the IceCube Observatory and count the coincidences of the generated samples and the true observations within a 2.5$^\circ$ angular separation with the $\textit{Fermi}$-LAT blazar sources. We also investigate blazars located within an angular separation smaller than the maximum positional error calculated on an event-by-event basis by incorporating the event-specific angular uncertainty in neutrino localization and analyze the characteristics of these blazars to assess their plausibility as neutrino sources. We find an excess of high-energy neutrino events from the directions of $\textit{Fermi}$ blazars beyond random coincidence, with a significance of 2.82$\sigma$. Among the fifteen blazars that lie within the neutrino error regions and have a maximum number of neutrino events around them, the sources 4FGL J0509.4+0542 and 4FGL J0852.2+2834 are identified as high energy neutrino source at 3$\sigma$ significance.
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