Characterizing Candidate Blazar Counterparts of the Ultra-high-energy Event KM3-230213A

High-energy astrophysical neutrinos serve as crucial messengers for understanding hadronic acceleration processes and identifying the origins of cosmic rays, with blazars among the most promising neutrino sources. The KM3NeT experiment reported the detection of an ultrahigh-energy neutrino with an energy estimate of ∼220 PeV, the most energetic yet observed. The neutrino arrival direction has a 99% confidence region of 3° radius centered at R.A. 94.3, decl. −7.8 (J2000). In this work, 17 candidate blazars located within this region are identified. Comprehensive new observations and archival data analysis for these sources are presented. The study provides a complete multiwavelength coverage across radio, optical, X-ray, and gamma-ray bands, including proprietary data and dedicated follow-up observations. This study highlights flaring behavior in several candidate counterparts. One object exhibits a radio flare coinciding with the neutrino arrival time, with a pre-trial chance probability of 0.26%. Only for this object, the chance probability could be quantified in a robust way. Another candidate displays a rising trend in X-ray flux in a 1 yr window around the neutrino arrival time, while a third undergoes a gamma-ray flare during the same period. Based on the observational findings presented here, while none of these candidates can conclusively be linked to the neutrino, the implications of a possible blazar origin for the KM3NeT event are discussed.

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Publication Details

Journal
University of Southern Denmark Research Portal (University of Southern Denmark)
Published
2026-09-14
DOI
https://doi.org/10.82135/tno-1033969
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

Characterizing Candidate Blazar Counterparts of the Ultra-high-energy Event KM3-230213A

T. Chiarusi, R Cocimano, E. Eckerová, F. Carenini et al.
University of Southern Denmark Research Portal (University of Southern Denmark)
Astrophysics and Cosmic Phenomena
article

Characterizing Candidate Blazar Counterparts of the Ultra-high-energy Event KM3-230213A

T. Chiarusi, R Cocimano, E. Eckerová, F. Carenini, D Diego-Tortosa, D. Calvo, T. Eberl, Z Bardačová, M. Bouta, E. Drakopoulou, L. Cerisy, S. Biagi, V. Cecchini, A. Capone, M. Ardid, A. Condorelli, R. Dallier, J. Aublin, C. Bozza, M. Bouwhuis, I. El Bojaddaini, O. Adriani, Y. Becherini, E. Buis, S. El Hedri, M. Alshamsi, S. Bottai, R. Buompane, L. Aphecetche, S. El Mentawi, J. G. Ducoin, I. Del Rosso, P. Castaldi, F. Benfenati Gualandi, A. R. Alhebsi, L. S. Di Mauro, M. Chabab, A. Eddymaoui, A. B. Bouasla, J. A. B. Coelho, S. Celli, M. Breuhaus, M. Boettcher, M. Bendahman, M. Eff, S. Cherubini, R. Clark, E. Berbee, G. De Wasseige, D. Drouhin, A. Coleiro, A. Chen, I. Di Palma, M. Benhassi, A. Albert, R. Dvornický, L. Bailly-Salins, M. Bennani, V. Bertin, S. Buson, P. Deguire, P. Duverne, B. Caiffi, P. Betti, F. Bretaudeau, A. Creusot, F. Badaracco, A. Ambrosone, C. Distefano, V. Decoene, R. M. Bozza, P. Coyle, B. Baret, J. Busto, A. F. Díaz, J. Brunner, M. Andre, A. Bariego-Quintana, J. Boumaaza, V. Carretero, R. Bruijn, D. M. Benoit, D. Dornic, D. Bonanno, S. Ardid, D. van Eijk, A. Domi, H. Brânzaş, G. Cuttone, F. Ameli, R. Coniglione, R. Bruno, S. Aiello, S. Alves Garre, T. van Eeden, A. De Benedittis, E. Berti, T. Cartraud, M. Circella, C. Donzaud
article en

Abstract

High-energy astrophysical neutrinos serve as crucial messengers for understanding hadronic acceleration processes and identifying the origins of cosmic rays, with blazars among the most promising neutrino sources. The KM3NeT experiment reported the detection of an ultrahigh-energy neutrino with an energy estimate of ∼220 PeV, the most energetic yet observed. The neutrino arrival direction has a 99% confidence region of 3° radius centered at R.A. 94.3, decl. −7.8 (J2000). In this work, 17 candidate blazars located within this region are identified. Comprehensive new observations and archival data analysis for these sources are presented. The study provides a complete multiwavelength coverage across radio, optical, X-ray, and gamma-ray bands, including proprietary data and dedicated follow-up observations. This study highlights flaring behavior in several candidate counterparts. One object exhibits a radio flare coinciding with the neutrino arrival time, with a pre-trial chance probability of 0.26%. Only for this object, the chance probability could be quantified in a robust way. Another candidate displays a rising trend in X-ray flux in a 1 yr window around the neutrino arrival time, while a third undergoes a gamma-ray flare during the same period. Based on the observational findings presented here, while none of these candidates can conclusively be linked to the neutrino, the implications of a possible blazar origin for the KM3NeT event are discussed.

University of Southern Denmark Research Portal (University of Southern Denmark)
National Science Foundation, National Aeronautics and Space Administration, John Templeton Foundation, Gordon and Betty Moore Foundation, Belgian American Educational Foundation, California Institute of Technology, Arab Fund for Economic and Social Development, Space Telescope Science Institute, National Radio Astronomy Observatory, European Space Agency, Agenția Națională pentru Cercetare și Dezvoltare, European Commission, Queen's University Belfast, Trinity College Dublin, Agence Nationale de la Recherche, Swinburne University of Technology, Grantová Agentura České Republiky, Fundacja na rzecz Nauki Polskiej, Fonds De La Recherche Scientifique - FNRS, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Queen's University, Generalitat Valenciana, Korea Astronomy and Space Science Institute, Khalifa University of Science, Technology and Research, Centre National de la Recherche Scientifique, Shota Rustaveli National Science Foundation, Agentúra na Podporu Výskumu a Vývoja, National Astronomical Observatory of Japan, Stockholms Universitet, Ministry of Science and Higher Education of the Russian Federation, Istituto Nazionale di Fisica Nucleare, Région Normandie, Agencia Nacional de Investigación y Desarrollo, National Science and Technology Council, ESI Group, Ministero dell'Università e della Ricerca, Jet Propulsion Laboratory, Goddard Space Flight Center, University of California, Los Angeles, Smithsonian Astrophysical Observatory, HORIZON EUROPE Framework Programme, Science and Technology Facilities Council, Deutsches Elektronen-Synchrotron, Russian Academy of Sciences, National Institutes of Natural Sciences, European Regional Development Fund, Agencia Estatal de Investigación, Labex UnivEarthS, Institut National de Physique Nucléaire et de Physique des Particules, Astrophysics Science Division, CHIST-ERA
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