Lepto-hadronic modeling of blazars associated with well-reconstructed high-energy neutrino events
Year: 2026
Type: article
Abstract: The association of active galactic nuclei (AGN) with high-energy neutrinos has been investigated in both population studies and individual source analyses. However, whether individual associations are driven by physical processes or arise from chance coincidences remains an open question. A sample of blazars, AGN with relativistic jets closely aligned with the line of sight, spatially consistent with IceCube high-energy events, provides a natural framework to address this question. By combining multifrequency observations with physically motivated emission models, it is possible to assess whether these sources can plausibly account for the detected neutrinos. We studied six blazars with single gamma-ray counterparts to well-reconstructed IceCAT-1 high-energy events, accounting for the improved localization expected from IceCAT-2, and compiled their multifrequency spectral energy distributions. We modeled these sources within a lepto-hadronic framework, exploring their parameter space in order to reproduce the observed emission while preferentially selecting solutions that maximize neutrino production. We find that the spectral energy distributions can be reproduced with compact emission regions close to the broad-line region with moderately high Doppler factors. The overall emission is generally dominated by leptonic processes with subdominant contributions from hadronic cascades, except for one source where the hadronic components become dominant in gamma-rays. For four of the six sources, the energy density of the relativistic particles is close to equipartition with the magnetic field. The predicted neutrino-detection rates reach up to per year, in most cases compatible with the observation of one IceCube high-energy event when accounting for Poisson statistics. We conclude that, while the sources in the sample are not expected to significantly contribute to the diffuse neutrino flux, their properties are consistent with being possible counterparts to individual neutrino events. This is driven by a significant contribution of external photon fields to the hadronic interaction rate, even for sources where these fields have previously only been considered as nonsignificant.
Source: Astronomy and Astrophysics
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, California Institute of Technology, Johns Hopkins University, Space Telescope Science Institute, European Space Agency, Queen's University Belfast, Durham University, Trinity College Dublin, Queen's University, National Central University, Stockholms Universitet, Eötvös Loránd Tudományegyetem, Max-Planck-Institut für Astronomie, Jet Propulsion Laboratory, Goddard Space Flight Center, Smithsonian Astrophysical Observatory, Science Mission Directorate, Science and Technology Facilities Council, European Research Council, Deutsches Elektronen-Synchrotron, Institut National de Physique Nucléaire et de Physique des Particules, Astrophysics Science Division, Planetary Science Division, Los Alamos National Laboratory
Awards: G1028008162, EARTH IS OCCASIONALLY STRUCK BY AN ASTEROID OR COMET LARGE ENOUGH TO CAUSE A SIGNIFICANT EXPLOSION AND LOSS OF LIFE. THE MOST LIKELY IMPACT IS BY A RELATIVELY SMALL OBJECT AND THE BEST MITIGATION STRATEGY MAY SIMPLY BE TO MOVE PEOPLE OUT OF THE WAY. WITH ENOUGH WARNING A SMALL ASTEROID IMPACT WOULD NOT CAUSE LOSS OF LIFE AND PORTABLE PROPERTY MIGHT EVEN BE PRESERVED. WE HAVE BUILT AN "EARLY WARNING" SYSTEM THAT PROVIDES A THREE WEEK NOTICE OF MOST 140M ASTEROIDS OR COMETS ON TRACK TO HIT THE EARTH AND A WEEK'S NOTICE FOR MOST 50M ASTEROIDS. THE SYSTEM HAS BEEN DESIGNED BUILT AND BROUGHT INTO OPERATION IN LESS THAN THREE YEARS AND IS EASILY REPLICABLE. THE "ASTEROID TERRESTRIAL-IMPACT LAST ALERT SYSTEM" (ATLAS) CURRENTLY COMPRISES TWO OBSERVATORIES SEPARATED BY ABOUT 100KM THAT CAN SCAN THE ENTIRE VISIBLE SKY MORE THAN TWICE A NIGHT TO MAGNITUDE 20. SOFTWARE AUTOMATICALLY REGISTERS COMPARISONS WITH THE UNCHANGING SKY AND IDENTIFIES EVERYTHING THAT HAS MOVED OR CHANGED. COMMUNICATION BETWEEN THE OBSERVATORIES AND THE IAU MINOR PLANET CENTER LOCKS DOWN THE ORBIT OF ANYTHING APPROACHING THE EARTH. THIS PROPOSAL SEEKS FUNDING TO CONTINUE OPERATIONS OF THE TWO ATLAS UNITS ALREADY BUILT AND TO CONSTRUCT TWO MORE UNITS FOR THE SOUTHERN HEMISPHERE. ATLAS IS COMPLEMENTARY TO MANY EXISTING SURVEYS FOR NEAR-EARTH OBJECTS (NEOS) BY VIRTUE OF BEING ALL-SKY: IT CAN DETECT MOST 140M NEOS THAT PASS WITHIN 0.1AU OF THE EARTH. ATLAS MAY FIND MORE THAN 500 NEOS PER YEAR EVEN THOUGH ITS FORTE IS DISCOVERY OF THE SUBSET OF NEOS THAT PASS VERY CLOSE TO THE EARTH. ITS STEADY SKY COVERAGE IS ALSO VALUABLE FOR DISCOVERY OF LOW DELTA-V ASTEROIDS CANDIDATE TARGETS FOR A MANNED MISSION. FURTHERMORE ATLAS WILL CHARACTERIZE THE NEO POPULATION AND ALL THE OTHER OBJECTS IT DETECTS BY OBTAINING HUNDREDS OF LIGHT CURVE POINTS PER YEAR THAT WILL ENABLE THE DETERMINATION OF THEIR SHAPE AND SPIN AND ALSO BY OBTAINING SIMULTANEOUS COLOR MEASUREMENTS. OBJECTIVES: ATLAS WILL 1) PROVIDE WARNING THAT IS USEFUL ON A CIVIL DEFENSE TIMESCALE FOR THE MAJORITY OF EARTH-IMPACTING ASTEROIDS OF 50M SIZE OR LARGER 2) REDISCOVER 50% OF ALL 1000M NEOS AND POTENTIALLY HAZARDOUS OBJECTS (PHO) WITHIN 1 YEAR 70% IN 3 YEARS AND 90% IN 10 YEARS DISCOVER MORE THAN 400 NEOS AND 100 PHOS PER YEAR OF 140M SIZE OR LARGER 3) DETECT ABOUT ONE SMALL ASTEROID PER YEAR THAT HITS THE EARTH 4) DISCOVER LOW DELTA-V ASTEROIDS 5) ENABLE SHAPE AND SPIN CALCULATIONS FROM HUNDREDS OF OBSERVATIONS PER YEAR OF THOUSANDS OF ASTEROIDS AND 6) DETECT ALL PLUTO-SIZED OBJECTS WITHIN A DISTANCE OF 120 AU. METHODS: WE HAVE BUILT A PAIR OF SMALL OBSERVATORIES EACH WITH AN 0.5M TELESCOPE THAT COVERS 30 SQUARE DEG WITH EACH EXPOSURE AND WE HAVE WRITTEN ALL THE SOFTWARE REQUIRED FOR THEM TO OPERATE WITHOUT HUMAN INTERVENTION. WE ARE CURRENTLY REPORTING ASTEROID AND COMET DETECTIONS TO THE MPC AND AS THE SYSTEM COMES FULLY ONLINE OUR RATE OF DISCOVERY WILL INCREASE BY A FACTOR OF 10. BY BUILDING ANOTHER TWO UNITS IN THE SOUTH AND AT DIFFERENT LONGITUDE WE WILL DOUBLE OUR DETECTION PROBABILITY FOR THE NEXT CHELYABINSKSIZED IMPACTOR. SIGNIFICANCE: THIS PROJECT WORKS TOWARDS ACCOMPLISHING THE CONGRESSIONAL MANDATE TO MITIGATE THE HAZARD FROM EARTH-IMPACTING ASTEROIDS BY FOCUSING ON DETECTION OF NEARLY ALL HAZARDOUS ASTEROIDS IN THE DAYS OR WEEKS BEFORE IMPACT. ALTHOUGH DETECTION IN TIME TO DIVERT DANGEROUS ASTEROIDS IS LAUDABLE IT IS ALSO CURRENTLY UNAFFORDABLE AND ATLAS ADDRESSES THE INTENT OF THE MANDATE BY PROTECTING LIVES. ATLAS WILL AFFORD A YEARLY OPPORTUNITY TO STUDY A METEORITE BEFORE IT STRIKES THE EARTH'S ATMOSPHERE AND WILL PROVIDE MUCH BETTER STATISTICS ON THE POPULATION THAT DOES PASS CLOSE TO THE EARTH. ATLAS WILL DISCOVER LOW DELTA-V ASTEROIDS SUITABLE FOR A MANNED MISSION AND CHARACTERIZATION OF THE SPIN AND SHAPE OF MANY ASTEROIDS MAY PROVE VALUABLE FOR FUTURE MISSIONS., Exploring & Exploiting the Dynamic Optical Sky, G2945741187, G3095507666, Queen's University Belfast Astronomy Observation and Theory Consolidated Grant 2020-2023, THE ASTEROID TERRESTRIAL-IMPACT LAST ALERT SYSTEM (ATLAS) WAS AWARDED A 5 YEAR GRANT BY NASA NEOO IN 2013 TO CONSTRUCT AND OPERATE WIDE FIELD TELESCOPES THAT ARE CAPABLE OF SCANNING THE ENTIRE SKY EACH NIGHT TO MAGNITUDE 20. THE PARTICULAR STRENGTH OF ATLAS IS TO BE COMPLEMENTARY TO LARGER TELESCOPES SUCH AS PAN-STARRS AND CATALINA - ATLAS COVERS MUCH MORE AREA EACH NIGHT TO A SHALLOWER DEPTH. ATLAS IS DESIGNED TO BE AN "EARLY WARNING" SYSTEM THAT WILL PROVIDE THREE WEEKS' NOTICE OF MOST 140M ASTEROIDS OR COMETS ON TRACK TO HIT THE EARTH AND A WEEK'S NOTICE FOR MOST 50M ASTEROIDS. WE HAVE COMPLETED TWO ATLAS UNITS AND INSTALLED THEM ON HALEAKALA AND MAUNA LOA IN HAWAII. THE TELESCOPES OPERATE COMPLETELY ROBOTICALLY EACH NIGHT AND THROUGHOUT THE NIGHT THE DATA ARE REDUCED IN REAL-TIME ON EACH SUMMIT AND ANALYZED FOR CANDIDATE NEAR-EARTH ASTEROIDS. IN THE MORNING A HUMAN REVIEWER VERIFIES THE NEW ASTEROIDS IN THE NIGHTLY PROCESSING AND SUBMITS ASTROMETRY TO THE IAU MINOR PLANET CENTER. WE OBSERVE ABOUT HALF THE VISIBLE SKY EACH NIGHT FIVE TIMES WITH THE TWO-TELESCOPE SYSTEM BUT AT REDUCED SENSITIVITY DUE TO IMPROPERLY FIGURED SCHMIDT CORRECTORS ON THE TELESCOPES. REPLACEMENT LENSES FROM A DIFFERENT VENDOR ARE EXPECTED TO BE INSTALLED IN APRIL 2017 IMPROVING THE SENSITIVITY OF THE SYSTEM FROM M~19 TO THE DESIGNED CAPABILITY OF M~20 AND INCREASING THE DISCOVERY RATE BY MORE THAN 5X. TO DATE IN EARLY 2017 ATLAS HAS DISCOVERED 34 NEAS AND 5 PHAS SINCE START OF OPERATIONS. EXCEPT FOR DELAYS DUE TO THE SCHMIDT CORRECTORS ALL OTHER ASPECTS OF THE BUILD CONSTRUCTION AND COMMISSIONING OF BOTH THE HARDWARE AND SOFTWARE PROJECTS HAVE BEEN ON-TIME AND ON-BUDGET. WE ARE PROPOSING TO BUILD TWO MORE IDENTICAL "ATLAS UNITS" AND DEPLOY THEM AT THE BEST SITES POSSIBLE. WE EXPECT THAT THESE SITES WILL BE SAAO IN SOUTH AFRICA AND CHILE BUT WE WILL PERFORM A COMPETITIVE SEARCH FOR ALTERNATE SITES ONCE THE PROPOSAL IS FUNDED. BECAUSE OF THE DIVERSITY IN LATITUDE LONGITUDE AND WEATHER THESE TWO ADDITIONAL UNITS SHOULD DOUBLE THE ATLAS DISCOVERY RATE OF THE MOST PERNICIOUS PHAS - THE 20-50M ASTEROIDS THAT PASS VERY CLOSE TO THE EARTH AND ARE ONLY VISIBLE TO ANY TELESCOPE FOR A SHORT TIME., G4056058649, G4474636675, G4576554894, UK Involvement in LSST: Phase B (QUB component), G4797677415, G4800998230, G6120759733, G6131798161, G618131832, G6389653479, G6549972864, A NEO SEARCH PROGRAM USING THE PAN-STARRS PS1 TELESCOPETHE GOAL OF THE PROPOSED RESEARCH IS TO USE T, G6900289228, G7187964967, G7258890752, Pan-STARRS1: Operations; Public Data Release; Education and Outreach, G8253295839, G833430883, G8429986923
OpenAlex ID: W7213604581