A lower bound on intergalactic magnetic fields from time variability of 1ES 0229+200 from MAGIC and Fermi/LAT observations

¹ Instituto de Astrofísica de Canarias and Dpto. de Astrofísica, Universidad de La Laguna, 38200 La Laguna, Tenerife, Spain
² National Institute for Astrophysics (INAF), 00136 Rome, Italy
³ Università di Udine and INFN Trieste, 33100 Udine, Italy
⁴ Max-Planck-Institut für Physik, 80805 München, Germany
⁵ Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra, Barcelona, Spain
⁶ Japanese MAGIC Group: Institute for Cosmic Ray Research (ICRR), The University of Tokyo, Kashiwa, 277-8582 Chiba, Japan
⁷ Technische Universität Dortmund, 44221 Dortmund, Germany
⁸ Croatian MAGIC Group: University of Zagreb, Faculty of Electrical Engineering and Computing (FER), 10000 Zagreb, Croatia
⁹ IPARCOS Institute and EMFTEL Department, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹⁰ Centro Brasileiro de Pesquisas Físicas (CBPF), 22290-180 URCA, Rio de Janeiro, RJ, Brazil
¹¹ Università di Padova and INFN, 35131 Padova, Italy
¹² University of Lodz, Faculty of Physics and Applied Informatics, Department of Astrophysics, 90-236 Lodz, Poland
¹³ Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
¹⁴ ETH Zürich, 8093 Zürich, Switzerland
¹⁵ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁶ Università di Pisa and INFN Pisa, 56126 Pisa, Italy
¹⁷ Universitat de Barcelona, ICCUB, IEEC-UB, 08028 Barcelona, Spain
¹⁸ Armenian MAGIC Group: A. Alikhanyan National Science Laboratory, 0036 Yerevan, Armenia
¹⁹ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, 28040 Madrid, Spain
²⁰ Department for Physics and Technology, University of Bergen, Bergen, Norway
²¹ INFN MAGIC Group: INFN Sezione di Catania and Dipartimento di Fisica e Astronomia, University of Catania, 95123 Catania, Italy
²² INFN MAGIC Group: INFN Sezione di Torino and Università degli Studi di Torino, 10125 Torino, Italy
²³ INFN MAGIC Group: INFN Sezione di Bari and Dipartimento Interateneo di Fisica dell’Università e del Politecnico di Bari, 70125 Bari, Italy
²⁴ Croatian MAGIC Group: University of Rijeka, Department of Physics, 51000 Rijeka, Croatia
²⁵ Universität Würzburg, 97074 Würzburg, Germany
²⁶ Finnish MAGIC Group: Finnish Centre for Astronomy with ESO, University of Turku, 20014 Turku, Finland
²⁷ Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
²⁸ Japanese MAGIC Group: Physics Program, Graduate School of Advanced Science and Engineering, Hiroshima University, 739-8526 Hiroshima, Japan
²⁹ Armenian MAGIC Group: ICRANet-Armenia at NAS RA, 0019 Yerevan, Armenia
³⁰ Croatian MAGIC Group: University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture (FESB), 21000 Split, Croatia
³¹ Croatian MAGIC Group: Josip Juraj Strossmayer University of Osijek, Department of Physics, 31000 Osijek, Croatia
³² Japanese MAGIC Group: Department of Physics, Kyoto University, 606-8502 Kyoto, Japan
³³ Japanese MAGIC Group: Department of Physics, Tokai University, Hiratsuka, 259-1292 Kanagawa, Japan
³⁴ Università di Siena and INFN Pisa, 53100 Siena, Italy
³⁵ Saha Institute of Nuclear Physics, HBNI, 1/AF Bidhannagar, Salt Lake, Sector-1, Kolkata 700064, India
³⁶ Inst. for Nucl. Research and Nucl. Energy, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
³⁷ Japanese MAGIC Group: Department of Physics, Yamagata University, Yamagata 990-8560, Japan
³⁸ Finnish MAGIC Group: Astronomy Research Unit, University of Oulu, 90014 Oulu, Finland
³⁹ Croatian MAGIC Group: Ruđer Bošković Institute, 10000 Zagreb, Croatia
⁴⁰ INFN MAGIC Group: INFN Sezione di Perugia, 06123 Perugia, Italy
⁴¹ INFN MAGIC Group: INFN Roma Tor Vergata, 00133 Roma, Italy
⁴² Japanese MAGIC Group: Department of Physics, Konan University, Kobe, Hyogo 658-8501, Japan
⁴³ International Center for Relativistic Astrophysics (ICRA), Rome, Italy
⁴⁴ University of Innsbruck, 6020 Innsbruck, Austria
⁴⁵ Port d’Informació Científica (PIC), 08193 Bellaterra, Barcelona, Spain
⁴⁶ Ruhr-Universität Bochum, Fakultät für Physik und Astronomie, Astronomisches Institut (AIRUB), 44801 Bochum, Germany
⁴⁷ Dipartimento di Fisica, Università di Trieste, 34127 Trieste, Italy
⁴⁸ Max-Planck-Institut für Physik, 80805 München, Germany
⁴⁹ INAF Trieste and Dept. of Physics and Astronomy, University of Bologna, Bologna, Italy
⁵⁰ Université de Paris, CNRS, Astroparticule et Cosmologie, 75006 Paris, France
⁵¹ Institute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary Prospect 7a, Moscow 117312, Russia
⁵² Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
⁵³ Laboratory of Astrophysics, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne, Switzerland
⁵⁴ National Research Nuclear University MEPHI (Moscow Engineering Physics Institute), Kashirskoe Highway 31, 115409 Moscow, Russia

Received: 27 May 2022
Accepted: 29 September 2022

Abstract

Context. Extended and delayed emission around distant TeV sources induced by the effects of propagation of γ ray s through the intergalactic medium can be used for the measurement of the intergalactic magnetic field (IGMF).

Aims. We search for delayed GeV emission from the hard-spectrum TeV γ-ray emitting blazar 1ES 0229+200, with the goal of detecting or constraining the IGMF-dependent secondary flux generated during the propagation of TeV γ rays through the intergalactic medium.

Methods. We analysed the most recent MAGIC observations over a 5 year time span, and complemented them with historic data of the H.E.S.S. and VERITAS telescopes, along with a 12-year-long exposure of the Fermi/LAT telescope. We used them to trace source evolution in the GeV–TeV band over a decade and a half. We used Monte Carlo simulations to predict the delayed secondary γ-ray flux, modulated by the source variability, as revealed by TeV-band observations. We then compared these predictions for various assumed IGMF strengths to all available measurements of the γ-ray flux evolution.

Results. We find that the source flux in the energy range above 200 GeV experiences variations around its average on the 14-year time span of observations. No evidence for the flux variability is found in the 1 − 100 GeV energy range accessible to Fermi/LAT. The non-detection of variability due to delayed emission from electromagnetic cascade developing in the intergalactic medium imposes a lower bound of B > 1.8 × 10⁻¹⁷ G for the long-correlation-length IGMF and B > 10⁻¹⁴ G for an IGMF of cosmological origin. Though weaker than the one previously derived from the analysis of Fermi/LAT data, this bound is more robust, being based on a conservative intrinsic source spectrum estimate and accounting for the details of source variability in the TeV energy band. We discuss implications of this bound for cosmological magnetic fields that might explain the baryon asymmetry of the Universe.