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Energy Spectrum of Ultrahigh-Energy Cosmic Rays across Declinations −90° to +44.8° as Measured at the Pierre Auger Observatory

A. Abdul Halim1, P. Abreu2, M. Aglietta3,4, I. Allekotte5, K. Almeida Cheminant6,7, A. Almela8,9, R. Aloisio10,11, J. Alvarez-Muñiz12, A. Ambrosone10 et al. (Pierre Auger Collaboration§)

A. Ambrosone10, J. Ammerman Yebra12, G. A. Anastasi13,14, L. Anchordoqui15, B. Andrada8, L. Andrade Dourado10,11, S. Andringa2, L. Apollonio16,17, C. Aramo18, E. Arnone19,4, J. C. Arteaga Velázquez20, P. Assis2, G. Avila21, E. Avocone22,11, A. Bakalova23, F. Barbato10,11, A. Bartz Mocellin24, J. A. Bellido1, C. Berat25, M. E. Bertaina19,4, M. Bianciotto19,4, P. L. Biermann26, V. Binet27, K. Bismark28,8, T. Bister7,6, J. Biteau29,30, J. Blazek23, J. Blümer31, M. Boháčová23, D. Boncioli22,11, C. Bonifazi32, L. Bonneau Arbeletche33, N. Borodai34, J. Brack35, P. G. Brichetto Orchera8,31, F. L. Briechle36, A. Bueno37, S. Buitink38, M. Buscemi14,13, M. Büsken28,8, A. Bwembya7,6, K. S. Caballero-Mora39, S. Cabana-Freire12, L. Caccianiga16,17, F. Campuzano40, J. Caraça-Valente24, R. Caruso13,14, A. Castellina3,4, F. Catalani41, G. Cataldi42, L. Cazon12, M. Cerda43, B. Čermáková31, A. Cermenati10,11, J. A. Chinellato33, J. Chudoba23, L. Chytka44, R. W. Clay1, A. C. Cobos Cerutti40, R. Colalillo45,18, R. Conceição2, G. Consolati17,46, M. Conte47,42, F. Convenga22,11, D. Correia dos Santos48, P. J. Costa2, C. E. Covault49, M. Cristinziani50, C. S. Cruz Sanchez51, S. Dasso52,53, K. Daumiller31, B. R. Dawson1, R. M. de Almeida48, E.-T. de Boone50, B. de Errico48, J. de Jesús8,31, S. J. de Jong7,6, J. R. T. de Mello Neto48, I. De Mitri10,11, J. de Oliveira54, D. de Oliveira Franco55, F. de Palma47,42, V. de Souza56, E. De Vito47,42, A. Del Popolo13,14, O. Deligny57, N. Denner23, L. Deval3,4, A. di Matteo4, C. Dobrigkeit33, J. C. D’Olivo58, L. M. Domingues Mendes59,2, Q. Dorosti50, J. C. dos Anjos59, R. C. dos Anjos60, J. Ebr23, F. Ellwanger31, R. Engel28,31, I. Epicoco47,42, M. Erdmann36, A. Etchegoyen8,9, C. Evoli10,11, H. Falcke7,61,6, G. Farrar62, A. C. Fauth33, T. Fehler50, F. Feldbusch63, A. Fernandes2, M. Fernandez64, B. Fick65, J. M. Figueira8, P. Filip28,8, A. Filipčič66,67, T. Fitoussi31, B. Flaggs68, T. Fodran7, A. Franco42, M. Freitas2, T. Fujii69,*, A. Fuster8,9, C. Galea7, B. García40, C. Gaudu70, P. L. Ghia57, U. Giaccari42, F. Gobbi43, F. Gollan8, G. Golup5, M. Gómez Berisso5, P. F. Gómez Vitale21, J. P. Gongora21, J. M. González5, N. González8, D. Góra34, A. Gorgi3,4, M. Gottowik31, F. Guarino45,18, G. P. Guedes71, E. Guido50, L. Gülzow31, S. Hahn28, P. Hamal23, M. R. Hampel8, P. Hansen51, V. M. Harvey1, A. Haungs31, T. Hebbeker36, C. Hojvat72, J. R. Hörandel7,6, P. Horvath44, M. Hrabovský44, T. Huege31,38, A. Insolia13,14, P. G. Isar73, M. Ismaiel7,6, P. Janecek23, V. Jilek23, K.-H. Kampert70, B. Keilhauer31, A. Khakurdikar7, V. V. Kizakke Covilakam8,31, H. O. Klages31, M. Kleifges63, J. Köhler31, F. Krieger36, M. Kubatova23, N. Kunka63, B. L. Lago74, N. Langner36, N. Leal8, M. A. Leigui de Oliveira75, Y. Lema-Capeans12, A. Letessier-Selvon76, I. Lhenry-Yvon57, L. Lopes2, J. P. Lundquist67, M. Mallamaci77,14, D. Mandat23, P. Mantsch72, F. M. Mariani16,17, A. G. Mariazzi51, I. C. Mariş64, G. Marsella77,14, D. Martello47,42, S. Martinelli31,8, M. A. Martins12, H.-J. Mathes31, J. Matthews78, G. Matthiae79,80, E. Mayotte24, S. Mayotte24, P. O. Mazur72, G. Medina-Tanco58, J. Meinert70, D. Melo8, A. Menshikov63, C. Merx31, S. Michal23, M. I. Micheletti27, L. Miramonti16,17, M. Mogarkar34, S. Mollerach5, F. Montanet25, L. Morejon70, K. Mulrey7,6, R. Mussa4, W. M. Namasaka70, S. Negi23, L. Nellen58, K. Nguyen65, G. Nicora81, M. Niechciol50, D. Nitz65, D. Nosek82, A. Novikov68, V. Novotny82, L. Nožka44, A. Nucita47,42, L. A. Núñez83, J. Ochoa8,31, C. Oliveira56, L. Östman23, M. Palatka23, J. Pallotta81, S. Panja23, G. Parente12, T. Paulsen70, J. Pawlowsky70, M. Pech23, J. Pȩkala34, R. Pelayo84, V. Pelgrims64, L. A. S. Pereira85, E. E. Pereira Martins28,8, C. Pérez Bertolli8,31, L. Perrone47,42, S. Petrera10,11, C. Petrucci22, T. Pierog31, M. Pimenta2, M. Platino8, B. Pont7, M. Pourmohammad Shahvar77,14, P. Privitera69, C. Priyadarshi34, M. Prouza23, K. Pytel86, S. Querchfeld70, J. Rautenberg70, D. Ravignani8, J. V. Reginatto Akim33, A. Reuzki36, J. Ridky23, F. Riehn12,†, M. Risse50, V. Rizi22,11, E. Rodriguez8,31, G. Rodriguez Fernandez80, J. Rodriguez Rojo21, S. Rossoni55, M. Roth31, E. Roulet5, A. C. Rovero52, A. Saftoiu87, M. Saharan7, F. Salamida22,11, H. Salazar88, G. Salina80, P. Sampathkumar31, N. San Martin24, J. D. Sanabria Gomez83, F. Sánchez8, E. M. Santos89, E. Santos23, F. Sarazin24, R. Sarmento2, R. Sato21, P. Savina10,11, V. Scherini47,42, H. Schieler31, M. Schimassek57, M. Schimp70, D. Schmidt31, O. Scholten38,‡, H. Schoorlemmer7,6, P. Schovánek23, F. G. Schröder68,31, J. Schulte36, T. Schulz23, S. J. Sciutto51, M. Scornavacche8,31, A. Sedoski8, A. Segreto90,14, S. Sehgal70, S. U. Shivashankara67, G. Sigl55, K. Simkova38,64, F. Simon63, R. Šmída69, P. Sommers91, R. Squartini43, M. Stadelmaier31,17,16, S. Stanič67, J. Stasielak34, P. Stassi25, S. Strähnz28, M. Straub36, T. Suomijärvi29, A. D. Supanitsky8, Z. Svozilikova23, K. Syrokvas82, Z. Szadkowski86, F. Tairli1, M. Tambone45,18, A. Tapia92, C. Taricco19,4, C. Timmermans6,7, O. Tkachenko23, P. Tobiska23, C. J. Todero Peixoto41, B. Tomé2, A. Travaini43, P. Travnicek23, M. Tueros51, M. Unger31, R. Uzeiroska70, L. Vaclavek44, M. Vacula44, I. Vaiman10,11, J. F. Valdés Galicia58, L. Valore45,18, P. van Dillen7,6, E. Varela88, V. Vašíčková70, A. Vásquez-Ramírez83, D. Veberič31, I. D. Vergara Quispe51, S. Verpoest68, V. Verzi80, J. Vicha23, J. Vink93, S. Vorobiov67, J. B. Vuta23, C. Watanabe48, A. A. Watson94, A. Weindl31, M. Weitz70, L. Wiencke24, H. Wilczyński34, B. Wundheiler8, B. Yue70, A. Yushkov23, E. Zas12, D. Zavrtanik67,66, and M. Zavrtanik66,67 (Pierre Auger Collaboration§)

  • 1University of Adelaide, Adelaide, South Australia, Australia
  • 2Laboratório de Instrumentação e Física Experimental de Partículas—LIP and Instituto Superior Técnico—IST, Universidade de Lisboa—UL, Lisboa, Portugal
  • 3Osservatorio Astrofisico di Torino (INAF), Torino, Italy
  • 4INFN, Sezione di Torino, Torino, Italy
  • 5Centro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), San Carlos de Bariloche, Argentina
  • 6Nationaal Instituut voor Kernfysica en Hoge Energie Fysica (NIKHEF), Science Park, Amsterdam, The Netherlands
  • 7IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands
  • 8Instituto de Tecnologías en Detección y Astropartículas (CNEA, CONICET, UNSAM), Buenos Aires, Argentina
  • 9Universidad Tecnológica Nacional—Facultad Regional Buenos Aires, Buenos Aires, Argentina
  • 10Gran Sasso Science Institute, L’Aquila, Italy
  • 11INFN Laboratori Nazionali del Gran Sasso, Assergi (L’Aquila), Italy
  • 12Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de Santiago de Compostela, Santiago de Compostela, Spain
  • 13Università di Catania, Dipartimento di Fisica e Astronomia “Ettore Majorana,” Catania, Italy
  • 14INFN, Sezione di Catania, Catania, Italy
  • 15Department of Physics and Astronomy, Lehman College, City University of New York, Bronx, NY, USA
  • 16Università di Milano, Dipartimento di Fisica, Milano, Italy
  • 17INFN, Sezione di Milano, Milano, Italy
  • 18INFN, Sezione di Napoli, Napoli, Italy
  • 19Università Torino, Dipartimento di Fisica, Torino, Italy
  • 20Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, México
  • 21Observatorio Pierre Auger and Comisión Nacional de Energía Atómica, Malargüe, Argentina
  • 22Università dell’Aquila, Dipartimento di Scienze Fisiche e Chimiche, L’Aquila, Italy
  • 23Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
  • 24Colorado School of Mines, Golden, Colorado, USA
  • 25Université Grenoble Alpes, CNRS, Grenoble Institute of Engineering Université Grenoble Alpes, LPSC-IN2P3, 38000 Grenoble, France
  • 26Max-Planck-Institut für Radioastronomie, Bonn, Germany
  • 27Instituto de Física de Rosario (IFIR)—CONICET/U.N.R. and Facultad de Ciencias Bioquímicas y Farmacéuticas U.N.R., Rosario, Argentina
  • 28Karlsruhe Institute of Technology (KIT), Institute for Experimental Particle Physics, Karlsruhe, Germany
  • 29Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • 30Institut universitaire de France (IUF), Paris, France
  • 31Karlsruhe Institute of Technology (KIT), Institute for Astroparticle Physics, Karlsruhe, Germany
  • 32International Center of Advanced Studies and Instituto de Ciencias Físicas, ECyT-UNSAM and CONICET, Campus Miguelete—San Martín, Buenos Aires, Argentina
  • 33Universidade Estadual de Campinas (UNICAMP), IFGW, Campinas, SP, Brazil
  • 34Institute of Nuclear Physics PAN, Krakow, Poland
  • 35Colorado State University, Fort Collins, Colorado, USA
  • 36RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany
  • 37Universidad de Granada and C.A.F.P.E., Granada, Spain
  • 38Vrije Universiteit Brussels, Brussels, Belgium
  • 39Universidad Autónoma de Chiapas, Tuxtla Gutiérrez, Chiapas, México
  • 40Instituto de Tecnologías en Detección y Astropartículas (CNEA, CONICET, UNSAM), and Universidad Tecnológica Nacional—Facultad Regional Mendoza (CONICET/CNEA), Mendoza, Argentina
  • 41Universidade de São Paulo, Escola de Engenharia de Lorena, Lorena, São Paulo, Brazil
  • 42INFN, Sezione di Lecce, Lecce, Italy
  • 43Observatorio Pierre Auger, Malargüe, Argentina
  • 44Palacky University, Olomouc, Czech Republic
  • 45Università di Napoli “Federico II,” Dipartimento di Fisica “Ettore Pancini,” Napoli, Italy
  • 46Politecnico di Milano, Dipartimento di Scienze e Tecnologie Aerospaziali, Milano, Italy
  • 47Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi,” Lecce, Italy
  • 48Universidade Federal do Rio de Janeiro, Instituto de Física, Rio de Janeiro, Rio de Janeiro, Brazil
  • 49Case Western Reserve University, Cleveland, Ohio, USA
  • 50Universität Siegen, Department Physik—Experimentelle Teilchenphysik, Siegen, Germany
  • 51IFLP, Universidad Nacional de La Plata and CONICET, La Plata, Argentina
  • 52Instituto de Astronomía y Física del Espacio (IAFE, CONICET-UBA), Buenos Aires, Argentina
  • 53Departamento de Física and Departamento de Ciencias de la Atmósfera y los Océanos, FCEyN, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina
  • 54Instituto Federal de Educação, Ciência e Tecnologia do Rio de Janeiro (IFRJ), Rio de Janeiro, Brazil
  • 55Universität Hamburg, II. Institut für Theoretische Physik, Hamburg, Germany
  • 56Universidade de São Paulo, Instituto de Física de São Carlos, São Carlos, São Paulo, Brazil
  • 57CNRS/IN2P3, IJCLab, Université Paris-Saclay, Orsay, France
  • 58Universidad Nacional Autónoma de México, México, DF, México
  • 59Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Rio de Janeiro, Brazil
  • 60Universidade Federal do Paraná, Setor Palotina, Palotina, Brazil
  • 61Stichting Astronomisch Onderzoek in Nederland (ASTRON), Dwingeloo, The Netherlands
  • 62New York University, New York, New York, USA
  • 63Karlsruhe Institute of Technology (KIT), Institut für Prozessdatenverarbeitung und Elektronik, Karlsruhe, Germany
  • 64Université Libre de Bruxelles (ULB), Brussels, Belgium
  • 65Michigan Technological University, Houghton, Michigan, USA
  • 66Experimental Particle Physics Department, Jožef Stefan Institute, Ljubljana, Slovenia
  • 67Center for Astrophysics and Cosmology (CAC), University of Nova Gorica, Nova Gorica, Slovenia
  • 68University of Delaware, Department of Physics and Astronomy, Bartol Research Institute, Newark, Delaware, USA
  • 69University of Chicago, Enrico Fermi Institute, Chicago, Illinois, USA
  • 70Bergische Universität Wuppertal, Department of Physics, Wuppertal, Germany
  • 71Universidade Estadual de Feira de Santana, Feira de Santana, Brazil
  • 72Fermi National Accelerator Laboratory, Fermilab, Batavia, Illinois, USA
  • 73Institute of Space Science, Bucharest-Magurele, Romania
  • 74Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Petropolis, Brazil
  • 75Universidade Federal do ABC, Santo André, São Paulo, Brazil
  • 76Laboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), Sorbonne Université, Université de Paris, CNRS-IN2P3, Paris, France
  • 77Università di Palermo, Dipartimento di Fisica e Chimica “E. Segrè,” Palermo, Italy
  • 78Louisiana State University, Baton Rouge, Louisiana, USA
  • 79Università di Roma “Tor Vergata,” Dipartimento di Fisica, Roma, Italy
  • 80INFN, Sezione di Roma “Tor Vergata,” Roma, Italy
  • 81Laboratorio Atmósfera—Departamento de Investigaciones en Láseres y sus Aplicaciones—UNIDEF (CITEDEF-CONICET), Buenos Aires, Argentina
  • 82Charles University, Faculty of Mathematics and Physics, Institute of Particle and Nuclear Physics, Prague, Czech Republic
  • 83Universidad Industrial de Santander, Bucaramanga, Colombia
  • 84Unidad Profesional Interdisciplinaria en Ingeniería y Tecnologías Avanzadas del Instituto Politécnico Nacional (UPIITA-IPN), México, DF, México
  • 85Universidade Federal de Campina Grande, Centro de Ciencias e Tecnologia, Campina Grande, Brazil
  • 86University of Łódź, Faculty of High-Energy Astrophysics, Łódź, Poland
  • 87“Horia Hulubei” National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, Romania
  • 88Benemérita Universidad Autónoma de Puebla, Puebla, México
  • 89Universidade de São Paulo, Instituto de Física, São Paulo, São Paulo, Brazil
  • 90Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo (INAF), Palermo, Italy
  • 91Pennsylvania State University, University Park, Pennsylvania, USA
  • 92Universidad de Medellín, Medellín, Colombia
  • 93Universiteit van Amsterdam, Faculty of Science, Amsterdam, The Netherlands
  • 94School of Physics and Astronomy, University of Leeds, Leeds, United Kingdom

  • *Present address: Graduate School of Science, Osaka Metropolitan University, Osaka, Japan.
  • †Present address: Technische Universität Dortmund and Ruhr-Universität Bochum, Dortmund and Bochum, Germany.
  • ‡Also at Kapteyn Institute, University of Groningen, Groningen, The Netherlands.
  • §Contact author: spokespersons@auger.org; http://www.auger.org

Phys. Rev. Lett. 135, 241002 – Published 9 December, 2025

DOI: https://doi.org/10.1103/p4l5-hxlf

Abstract

The energy spectrum of cosmic rays above 2.5 EeV has been measured across the declination range −90°≤δ≤+44.8° using ∼310 000 events accrued at the Pierre Auger Observatory from an exposure of (104 900±3 100)  km2 sr yr. No significant variations of energy spectra with declination are observed, after allowing or not for nonuniformities across the sky arising from the well-established dipolar anisotropies in the arrival directions of ultrahigh-energy cosmic rays. The instep feature in the spectrum at ≃10  EeV reported previously is now established at a significance above 5σ. Within the statistics, the energy spectra are indistinguishable across declinations so disfavoring an origin for the instep from a few distinctive sources.

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synopsis

A Large-Area Survey of Ultrahigh-Energy Cosmic Rays

Published 9 December, 2025

New measurements from an observatory in Argentina suggest that all the most energetic cosmic rays arise from the same types of extragalactic accelerators.

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