Bibcode
Eisenberger, L.; Bretz, T.; Dorner, D.; Brand, K.; Abhir, J.; Biland, A.; Elsaesser, D.; Günther, P.; Hasan, S.; Hildebrand, D.; Mannheim, K.; Linhoff, M.; Pfeifle, F.; Rhode, W.; Schleicher, B.; Sliusar, V.; Vorbrugg, M.; Walter, R.; Fact Collaboration; Aharonian, F.; Ait Benkhali, F.; Aschersleben, J.; Ashkar, H.; Backes, M.; Barbosa Martins, V.; Batzofin, R.; Becherini, Y.; Berge, D.; Böttcher, M.; Boisson, C.; Bolmont, J.; Borowska, J.; Brose, R.; Brown, A.; Brun, F.; Bruno, B.; Casanova, S.; Celic, J.; Cerruti, M.; Chen, A.; Chernyakova, M.; Chibueze, J.; Chibueze, O.; Cornejo, B.; Cotter, G.; Cozzolongo, G.; Damascene Mbarubucyeye, J.; de Assis Scarpin, J.; Delgado Giles, A.; Djannati-Ataï, A.; Djuvsland, J.; Dmytriiev, A.; Egberts, K.; Egg, K.; Einecke, S.; Ernenwein, J.-P.; Escañuela Nieves, C.; Feijen, K.; Filipovic, M.; Fontaine, G.; Funk, S.; Gabici, S.; Glicenstein, J. F.; Goswami, P.; Grolleron, G.; Hess, B.; Hinton, J. A.; Holler, M.; Jamrozy, M.; Jankowsky, F.; Jung-Richardt, I.; Kasai, E.; Katarzyński, K.; Katjaita, H.; Kerszberg, D.; Khatoon, R.; Khélifi, B.; Kluźniak, W.; Komin, Nu.; Konno, R.; Kosack, K.; Kostunin, D.; Kukec Mezek, G.; Lang, R. G.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Luashvili, A.; Mackey, J.; Marandon, V.; Martí-Devesa, G.; Marx, R.; Mayer, M.; Mehta, A.; Mitchell, A.; Moderski, R.; Moghadam, M. O.; Mohrmann, L.; Moulin, E.; de Naurois, M. et al.
Bibliographical reference
The Astrophysical Journal
Advertised on:
2
2026
Journal
Refereed citations
0
Description
The search for sources of high-energy astrophysical neutrinos can be significantly advanced through a multimessenger approach, which seeks to detect the γ-rays that accompany neutrinos as they are produced at their sources. Multimessenger observations have so far provided the first evidence for a neutrino source, illustrated by the joint detection of the flaring blazar TXS 0506+056 in high-energy (E > 1 GeV) and very-high-energy (VHE; E > 100 GeV) γ-rays in coincidence with the high-energy neutrino IceCube-170922A, identified by IceCube. Imaging atmospheric Cherenkov telescopes (IACTs), namely FACT, H.E.S.S., MAGIC, and VERITAS, continue to conduct extensive neutrino target-of-opportunity follow-up programs. These programs have two components: follow-up observations of single astrophysical neutrino candidate events (such as IceCube-170922A), and observation of known γ-ray sources after the identification of a cluster of neutrino events by IceCube. Here we present a comprehensive analysis of follow-up observations of high-energy neutrino events observed by the four IACTs between 2017 September (after the IceCube-170922A event) and 2021 January. Our study found no associations between γ-ray sources and the observed neutrino events. We provide a detailed overview of each neutrino event and its potential counterparts. Furthermore, a joint analysis of all IACT data is included, yielding combined upper limits on the VHE γ-ray flux.