Search for Ultra-high-energy Neutrons from Galactic Sources with the Pierre Auger Observatory

Abstract Deflections in the propagation of charged ultra-high-energy cosmic rays (UHECRs) caused by magnetic fields make the identification of their sources challenging. On the other hand, the arrival directions at Earth of neutrons point directly to their origin. The emission of UHECRs from a source is expected to be accompanied by the production of neutrons in its vicinity through interactions with ambient matter and radiation. Since free neutrons travel a mean distance d kpc −1 = 9.2 ( E EeV −1 ) before decaying, a neutron flux in the EeV range could be detected on Earth from sources of UHECRs in our Galaxy. Using cosmic-ray data from Phase I of the Surface Detector of the Pierre Auger Observatory, we search for neutron fluxes from Galactic candidate sources. We select more than 1000 objects of astrophysical interest, stacking them into target sets. The targets all have decl. within the exposure of the Observatory, ranging from −90° up to +45° for energies above 1 EeV (and up to +20° for energies down to 0.1 EeV). Given that a neutron air shower is indistinguishable from a proton one, there is a significant background due to cosmic rays. A neutron flux from the direction of a candidate source would be identified by a celestial density of events that significantly exceeds the expected density of cosmic rays for that direction. No significant excess is found at any tested target direction, and an upper limit on the neutron flux is calculated for each candidate source.

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Publication Details

Journal
The Astrophysical Journal
Published
2026-03-02
DOI
https://doi.org/10.3847/1538-4357/ae3f05
Primary Topic
Astrophysics and Cosmic Phenomena
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article
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0.00

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article

Search for Ultra-high-energy Neutrons from Galactic Sources with the Pierre Auger Observatory

M. Tambone, B. Andrada, U. Giaccari, L. Caccianiga et al.
The Astrophysical Journal
Astrophysics and Cosmic Phenomena
article

Search for Ultra-high-energy Neutrons from Galactic Sources with the Pierre Auger Observatory

M. Tambone, B. Andrada, U. Giaccari, L. Caccianiga, R. Squartini, C. Taricco, M. Olegario, S. Mancuso, M. R. Hampel, J. Stasielak, A. Filipčič, M. Büsken, S. Soares Sippert, V. de Souza, H. Falcke, K. -H. Kampert, K. Mulrey, G. Avila, M. Boháčová, L. Chytka, T. Bister, B. Yue, J. P. Gongora, E. De Vito, H. Schoorlemmer, N. Leal, B. L. Lago, C. Dobrigkeit, F. Campuzano, R. M. de Almeida, R. Caruso, Y. Dominguez Ballesteros, P. Sampathkumar, J. B. Vuta, S. J. Sciutto, F. Sarazin, L. Apollonio, G. Consolati, A. A. Novikov, Y. Lema-Capeans, A. Haungs, S. Buitink, A. Tapia, D. de Oliveira Franco, N. San Martin, L. Deval, J. Schulte, C. Priyadarshi, A. Fuster, G. Golup, A. Baluta, S. J. de Jong, A. C. Fauth, A. Khakurdikar, K. Bismark, F. Convenga, J. Biteau, L. Wiencke, J. Ochoa, C. Timmermans, H. Schieler, M. Mallamaci, F. G. Schröder, K. Pytel, A. Bueno, D. Nosek, Z. Szadkowski, C. Evoli, F. Ellwanger, I. Lhenry-Yvon, A. Ambrosone, B. Keilhauer, A. C. Cobos Cerutti, C. Pérez Bertolli, S. Hahn, M. Conte, C. Aramo, M. A. Martins, P. Horvath, R. W. Clay, S. E. Nuza, A. Etchegoyen, T. Hebbeker, D. Nitz, J. Alvarez-Muñiz, J. P. Lundquist, G. Parente, A. Letessier-Selvon, N. Borodai, F. Montanet, I. Vaiman, L. Cazon, P. Janecek, M. Freitas, P. G. Isar, W. M. Namasaka, G. Matthiae, F. Salamida, Q. Dorosti, L. Anchordoqui, S. Rossoni, S. Querchfeld, A. Almela, A. D. Supanitsky, S. Panja, M. Schimp, B. García, M. Ismaiel, P. Sommers, A. Insolia, T. Fujii, F. Riehn, B. de Errico, P. Hansen, R. Pelayo, P. van Dillen, L. Miramonti, C. Oliveira, D. Correia dos Santos, V. Pelgrims, G. Marsella, F. Krieger, P. Tobiska, L. Vaclavek, A. Menshikov, H. Salazar, J. Köhler, E. Mayotte, L. Gülzow, J. R. T. de Mello Neto, M. Kleifges, E. Arnone, M. Gómez Berisso, A. Bartz Mocellin, S. Strähnz, J. A. Matthews, J. Brack, J. M. Figueira, H. Wilczyński, J. Rautenberg, N. Langner, K. Daumiller, P. Schovánek, J. Blazek, M. Pech, P. Assis, O. Deligny, S. Negi, R. C. dos Anjos, D. Zavrtanik, B. Čermáková, N. González, M. Roth, D. Góra, J. Meinert, L. M. Domingues Mendes, R. Sarmento, A. A. Watson, M. Fernández Alonso, N. Denner, F. Sánchez, M. Gottowik, S. Martinelli, T. Paulsen, E. Varela, M. Tueros, M. Stadelmaier, J. D. Sanabria Gomez, T. Fodran, N. Kunka, C. Glaser, J. V. Reginatto Akim, K. Simkova, I. Allekotte, A. Del Popolo, C. Galea, P. Abreu, E. Zas, S. Petrera, A. Yushkov, F. Barbato, K. Denner Syrokvas, S. Stanič, S. Dasso, A. Reuzki, D. Veberič, O. Tkachenko, D. Martello, M. Schimassek, P. G. Brichetto Orchera, E. Roulet, P. Stassi, V. M. Harvey, M. Pimenta, C. S. Cruz Sanchez, C. Merx, G. Medina-Tanco, M. Mogarkar, M. A. Leigui de Oliveira, R. Šmída, M. Niechciol, L. Nožka, B. Flaggs, L. Perrone, M. Palatka, S. Mayotte, P. J. Costa, L. Östman, B. Wundheiler, P. Trávníček, M. Cerda, C. E. Covault, D. Melo, J. A. Chinellato, J. C. Arteaga Velázquez, E. Avocone, A. Weindl, A. Nucita, P. O. Mazur, C. Berat, G. Farrar, G. P. Guedes, B. R. Dawson, J. Blümer, G. Sigl, A. di Matteo, A. Vásquez-Ramírez, L. Lopes, J. F. Valdés Galicia, F. Catalani, K. Cerny, C. Gaudu, M. Prouza, M. Straub, J. Rodriguez Rojo, F. M. Mariani, P. L. Ghia, J. M. González, J. R. Hörandel, B. Fick, J. de Jesús, T. Pierog, V. Jilek, A. C. Rovero, P. Savina, M. Hrabovský, P. Privitera, A. Castellina, J. Ridky, P. Hamal, A. Abdul Halim, A. Sedoski, E. E. Pereira Martins, V. Verzi, A. Franco, R. Aloisio, H. -J. Mathes, V. Binet, S. Mollerach, J. Pękala, M. Scornavacche, M. Risse, K. Almeida Cheminant, T. Fitoussi, G. Nicora, M. Aglietta, S. Michal, C. Bonifazi, I. Epicoco, R. Engel, M. Vacula, E. Rodriguez, M. Pourmohammad Shahvar, F. Guarino, O. Scholten, C. Petrucci, V. Novotny, S. Verpoest, F. Simon, C. Trimarelli, L. Andrade Dourado, T. Fehler, T. Schulz, V. V. Kizakke Covilakam, A. G. Mariazzi, J. Vícha, A. Bakalová, J. Pawlowsky, F. Tairli, P. F. Gómez Vitale, M. Cristinziani, S. Sehgal, A. Saftoiu, F. de Palma, F. Gollan, M. Bianciotto, G. Rodriguez Fernandez, K. Nguyen, G. Cataldi, G. Salina, A. Bwembya, E. -T. de Boone, M. Saharan, M. Kubatova, P. Mantsch, T. Huege, A. Fernandes, H. O. Klages, E. Santos, J. C. D'Olivo, J. Caraça-Valente, V. Rizi, C. Hojvat, A. Gorgi, P. L. Biermann, I. De Mitri, M. Erdmann, M. I. Micheletti, F. Feldbusch, B. Pont, R. Conceição, V. Vašíčková, D. Ravignani, J. Ammerman Yebra, S. Cabana-Freire, I. D. Vergara Quispe, J. Pallotta, R. Mussa, L. Morejon, D. Schmidt, F. Gobbi, T. Suomijärvi, V. Scherini, M. Platino, L. A. Núñez, B. Tomé, L. Valore, R. Colalillo, R. Sato, K. S. Caballero-Mora, R. Uzeiroska, A. Travaini, M. Weitz, D. Boncioli, Z. Svozilikova, J. Chudoba, L. Nellen, C. J. Todero Peixoto, D. Mandat, P. Filip, J. Ebr, M. E. Bertaina, A. Cermenati, S. Vorobiov, I. C. Mariş, M. Unger, C. Watanabe, S. U. Shivashankara
article en

Abstract

Abstract Deflections in the propagation of charged ultra-high-energy cosmic rays (UHECRs) caused by magnetic fields make the identification of their sources challenging. On the other hand, the arrival directions at Earth of neutrons point directly to their origin. The emission of UHECRs from a source is expected to be accompanied by the production of neutrons in its vicinity through interactions with ambient matter and radiation. Since free neutrons travel a mean distance d kpc −1 = 9.2 ( E EeV −1 ) before decaying, a neutron flux in the EeV range could be detected on Earth from sources of UHECRs in our Galaxy. Using cosmic-ray data from Phase I of the Surface Detector of the Pierre Auger Observatory, we search for neutron fluxes from Galactic candidate sources. We select more than 1000 objects of astrophysical interest, stacking them into target sets. The targets all have decl. within the exposure of the Observatory, ranging from −90° up to +45° for energies above 1 EeV (and up to +20° for energies down to 0.1 EeV). Given that a neutron air shower is indistinguishable from a proton one, there is a significant background due to cosmic rays. A neutron flux from the direction of a candidate source would be identified by a celestial density of events that significantly exceeds the expected density of cosmic rays for that direction. No significant excess is found at any tested target direction, and an upper limit on the neutron flux is calculated for each candidate source.

The Astrophysical JournalVol. 999(2)
National Science Foundation, U.S. Department of Energy, Grainger Foundation, Strong, Ministerul Cercetării, Inovării şi Digitalizării, European Commission, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, Fundação de Amparo à Pesquisa do Estado de São Paulo, Ministerstvo Školství, Mládeže a Tělovýchovy, Grantová Agentura České Republiky, Bundesministerium für Bildung und Forschung, Fonds De La Recherche Scientifique - FNRS, Consejo Nacional de Investigaciones Científicas y Técnicas, Fonds Wetenschappelijk Onderzoek, Consejo Nacional de Ciencia y Tecnología, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Javna Agencija za Raziskovalno Dejavnost RS, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Centre National de la Recherche Scientifique, Financiadora de Estudos e Projetos, Ministerio de Ciencia e Innovación, Istituto Nazionale di Astrofisica, Universidad Nacional Autónoma de México, Benemérita Universidad Autónoma de Puebla, Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii, Xunta de Galicia, Junta de Andalucía, Ministério da Ciência, Tecnologia, Inovações e Comunicações, Vlaamse regering, Istituto Nazionale di Fisica Nucleare, Ministerium für Kultur und Wissenschaft des Landes Nordrhein-Westfalen, Helmholtz Alliance for Astroparticle Physics, Ministero dell'Università e della Ricerca, Fundação para a Ciência e a Tecnologia, Agencia Nacional de Promoción Científica y Tecnológica, Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México, European Regional Development Fund, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules
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