Speaker
Description
The origin of the remarkable ultra high energy neutrino event KM3-230213A observed with the ARCA detector is still unclear. In particular, most galactic scenarios are excluded, and a persistent isotropic source is disfavored due to the non-observation of a similar event by the IceCube detector. We show that the neutrino causing the KM3-230213A event could have been produced in the blazar PKS 0605-085 (redshift z = 0.87). This flat-spectrum radio quasar (FSRQ) is located at 2.4$^{\circ}$ from the reconstructed direction of the KM3-230213A event, allowing for an angular association between the blazar and the event in view of a sizable direction systematic uncertainty of 1.5$^{\circ}$ reported by the KM3Net Collaboration. FSRQs are believed to contain several distinct regions filled with photon fields external to the main relativistically moving particle acceleration zone (the "blob"), greatly boosting the neutrino production efficiency w.r.t. the synchrotron self-Compton (SSC) scenario. In particular, we consider a scenario where the external photon field is provided by the outer layer (the "sheath") of the "spine-sheath" jet structure, and particle acceleration occurs inside the same blobs that are responsible for the 2021-2023 gamma-ray flare of the blazar PKS 0605-085. Furthermore, we note that the X-ray and gamma-ray constraints on the produced neutrino intensity could be significantly relaxed in the framework of the external photon field scenario. We indicate a possible physical reason why the brightest blazar flares, notably from the blazar 3C 454.3, seem to be neutrino-dim. Following our previous work [A&A, 603, A59 (2017)]; [Phys. Rev. D, 102, 123017 (2020)]; [MNRAS, 505, 1940 (2021)]; [MNRAS, 527, L95 (2024)] we show that the intergalactic cascade gamma-ray counterpart of the KM3-230213A event is not observable by the existing gamma-ray telescopes in the considered scenario. Finally, we make a verifiable prediction that after the planned re-calibration of the ARCA detector the new, refined direction of the KM3-230213A event will point to the blazar PKS 0605-085. Some details of this work are available in astro-ph/2502.11434. This work is supported in the framework of the State project "Science" by the Ministry of Science and Higher Education of the Russian Federation under the contract 075-15-2024-541.