Searches for Neutrinos in the Direction of Radio-bright Blazars with the ANTARES Telescope

Abstract

Active galaxies, especially blazars, are among the most promising extragalactic candidates for high-energy neutrino sources. To date, ANTARES searches included these objects and used GeV–TeV γ-ray flux to select blazars. Here, a statistically complete blazar sample selected by their bright radio emission is used as the target for searches of origins of neutrinos collected by the ANTARES neutrino telescope over 13 yr of operation. The hypothesis of a neutrino–blazar directional correlation is tested by pair counting and a complementary likelihood-based approach. The resulting posttrial p-value is 3.0% (2.2σ in the two-sided convention). Additionally, a time-dependent analysis is performed to search for temporal clustering of neutrino candidates as a means of detecting neutrino flares in blazars. None of the investigated sources alone reaches a significant flare detection level. However, the presence of 18 sources with a pretrial significance above 3σ indicates a p = 1.4% (2.5σ in the two-sided convention) detection of a time-variable neutrino flux. An a posteriori investigation reveals an intriguing temporal coincidence of neutrino, radio, and γ-ray flares of the J0242+1101 blazar at a p = 0.5% (2.9σ in the two-sided convention) level. Altogether, the results presented here suggest a possible connection of neutrino candidates detected by the ANTARES telescope with radio-bright blazars.

Hard X-ray emission from blazars associated with high-energy neutrinos

“…Earlier statistical associations of neutrinos with bright blazars strongly link neutrino production to the very central parsec-scale regions of blazars [e.g., [9][10][11]13]. Still, observational…”

“…the neutrino association with radio blazars is starting to come from ANTARES [11] and Baikal-GVD [12] experiments. Additionally, [9] found that these high-energy neutrino events coincide with radio flares of the associated blazars, for which radio light curves are available.…”

“…We determine the spatial correlation by counting pairs of neutrino -blazar matches within the neutrino localization errors as defined in section 2. This is a commonly used approach based on the correlation function, recently applied for neutrino-blazar correlation in [11]. Correlation significance is evaluated through Monte-Carlo simulations: we generate random 10 5 realizations by scrambling the Right Ascension of all IceCube events while keeping their Declinations constant.…”

All-sky Search for Transient Astrophysical Neutrino Emission with 10 Years of IceCube Cascade Events

“…An archival search of 9.5 yr of IceCube data found further evidence at a statistical significance of 3.5σ for a neutrino flare that occurred between 2014 September and 2015 March that was not coincident with gamma-ray emission (Aartsen et al 2018b). Since then, further searches (Allakhverdyan et al 2023;Albert et al 2024) have hinted at the possible connection of neutrino flares and blazars. IceCube observed evidence for continuous neutrino emission from the Seyfert galaxy NGC 1068 with a significance of 4.2σ (Abbasi et al 2022).…”