Broadband multi-wavelength properties of M87 during the 2018 EHT campaign including a very high energy flaring episode

¹ Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
² Yale Center for Astronomy & Astrophysics, 52 Hillhouse Avenue, New Haven, CT 06511, USA
³ Department of Physics, Yale University, P.O. Box 2018120, New Haven, CT 06520, USA
⁴ Centre for Space Research, North-West University, Potchefstroom 2520, South Africa
⁵ Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu, Daejeon 34055, Republic of Korea
⁶ University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea
⁷ Research Center for Astronomical Computing, Zhejiang Lab, Hangzhou 311100, People’s Republic of China
⁸ INAF Istituto di Radioastronomia, Via P. Gobetti, 101, I-40129 Bologna, Italy
⁹ 525 Davey Laboratory, Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
¹⁰ Department of Physics, McGill University, 3600 University Street, Montréal, QC H3A 2T8, Canada
¹¹ Trottier Space Institute at McGill, 3550 University Street, Montréal, QC H3A 2A7, Canada
¹² Department of Astrophysics, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
¹³ Leiden Observatory–Allegro, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands
¹⁴ Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA 02138, USA
¹⁵ Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
¹⁶ Astronomical Science Program, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁷ Graduate School of Science, Nagoya City University, Yamanohata 1, Mizuho-cho, Mizuho-ku, Nagoya, 467-8501 Aichi, Japan
¹⁸ McGill Space Institute, McGill University, 3550 University Street, Montréal, QC H3A 2A7, Canada
¹⁹ Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, 02215 MA, USA
²⁰ Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
²¹ Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan
²² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
²³ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
²⁴ Kogakuin University of Technology & Engineering, Academic Support Center, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
²⁵ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s Republic of China
²⁶ Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, People’s Republic of China
²⁷ API–Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
²⁸ GRAPPA–Gravitation and AstroParticle Physics Amsterdam, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
²⁹ Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
³⁰ Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 1800 Sherman Ave, Evanston, IL 60201, USA
³¹ Department of Physics, Villanova University, 800 E. Lancaster Avenue, Villanova, PA 19085, USA
³² Physics Department, Washington University, CB 1105, St Louis, MO 63130, USA
³³ Dipartimento di Fisica, Università di Trieste, I-34127 Trieste, Italy
³⁴ Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste, Italy
³⁵ Finnish Centre for Astronomy with ESO, FI-20014 University of Turku, Finland
³⁶ Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
³⁷ Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA
³⁸ Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
³⁹ Massachusetts Institute of Technology Haystack Observatory, 99 Millstone Road, Westford, MA 01886, USA
⁴⁰ Black Hole Initiative at Harvard University, 20 Garden Street, Cambridge, MA 02138, USA
⁴¹ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain
⁴² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
⁴³ Department of Physics & Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
⁴⁴ Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan R.O.C.
⁴⁵ Departament d’Astronomia i Astrofísica, Universitat de Valéncia, C. Dr. Moliner 50, E-46100 Burjassot, Valéncia, Spain
⁴⁶ Observatori Astronómic, Universitat de València, C. Catedrático José Beltrán 2, E-46980 Paterna, València, Spain
⁴⁷ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala, Sweden
⁴⁸ Steward Observatory and Department of Astronomy, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
⁴⁹ Astronomy Department, Universidad de Concepción, Casilla 160-C, Concepción, Chile
⁵⁰ Department of Physics, University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA
⁵¹ Fermi National Accelerator Laboratory, MS209, P.O. Box 500 Batavia, IL 60510, USA
⁵² Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
⁵³ East Asian Observatory, 660 N. A’ohoku Place, Hilo, HI 96720, USA
⁵⁴ James Clerk Maxwell Telescope (JCMT), 660 N. A’ohoku Place, Hilo, HI 96720, USA
⁵⁵ California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA
⁵⁶ Institute of Astronomy and Astrophysics, Academia Sinica, 645 N. A’ohoku Place, Hilo, HI 96720, USA
⁵⁷ Department of Physics and Astronomy, University of Hawaii at Manoa, 2505 Correa Road, Honolulu, HI 96822, USA
⁵⁸ Department of Physics, McGill University, 3600 rue University, Montréal, QC H3A 2T8, Canada
⁵⁹ Trottier Space Institute at McGill, 3550 rue University, Montréal, QC H3A 2A7, Canada
⁶⁰ Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, F-38406 Saint Martin d’Hères, France
⁶¹ Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5, Canada
⁶² Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
⁶³ Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
⁶⁴ Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
⁶⁵ Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
⁶⁶ Department of Physics, University of Chicago, 5720 South Ellis Avenue, Chicago, IL 60637, USA
⁶⁷ Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
⁶⁸ Princeton Gravity Initiative, Jadwin Hall, Princeton University, Princeton, NJ 08544, USA
⁶⁹ Data Science Institute, University of Arizona, 1230 N. Cherry Ave., Tucson, AZ 85721, USA
⁷⁰ Program in Applied Mathematics, University of Arizona, 617 N. Santa Rita, Tucson, AZ 85721, USA
⁷¹ Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14853, USA
⁷² Department of Astronomy, Yonsei University, Yonsei-ro 50, Seodaemun-gu, 03722 Seoul, Republic of Korea
⁷³ Physics Department, Fairfield University, 1073 North Benson Road, Fairfield, CT 06824, USA
⁷⁴ Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801, USA
⁷⁵ Instituto de Astronomía, Universidad Nacional Autónoma de México (UNAM), Apdo Postal 70-264, Ciudad de Mexico, Mexico
⁷⁶ Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, D-60438 Frankfurt am Main, Germany
⁷⁷ Research Center for Intelligent Computing Platforms, Zhejiang Laboratory, Hangzhou 311100, China
⁷⁸ Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shengrong Road 520, Shanghai 201210, People’s Republic of China
⁷⁹ Department of Astronomy and Columbia Astrophysics Laboratory, Columbia University, 500 W. 120th Street, New York, NY 10027, USA
⁸⁰ Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
⁸¹ Dipartimento di Fisica “E. Pancini”, Università di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli, Italy
⁸² INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli, Italy
⁸³ Wits Centre for Astrophysics, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, Johannesburg 2050, South Africa
⁸⁴ Department of Physics, University of Pretoria, Hatfield, Pretoria 0028, South Africa
⁸⁵ Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Makhanda 6140, South Africa
⁸⁶ ASTRON, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands
⁸⁷ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, F-92195 Meudon, France
⁸⁸ JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA
⁸⁹ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, PR China
⁹⁰ Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA
⁹¹ Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
⁹² National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
⁹³ Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 32-D476, 77 Massachusetts Ave., Cambridge, MA 02142, USA
⁹⁴ Google Research, 355 Main St., Cambridge, MA 02142, USA
⁹⁵ Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Str. 31, D-97074 Würzburg, Germany
⁹⁶ Department of History of Science, Harvard University, Cambridge, MA 02138, USA
⁹⁷ Department of Physics, Harvard University, Cambridge, MA 02138, USA
⁹⁸ NCSA, University of Illinois, 1205 W. Clark St., Urbana, IL 61801, USA
⁹⁹ Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090, Brazil
¹⁰⁰ CP3-Origins, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
¹⁰¹ Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51 y 216, 72000 Puebla Pue., Mexico
¹⁰² Consejo Nacional de Humanidades, Ciencia y Tecnología, Av. Insurgentes Sur 1582, 03940 Ciudad de México, Mexico
¹⁰³ Key Laboratory for Research in Galaxies and Cosmology, Chinese Academy of Sciences, Shanghai 200030, People’s Republic of China
¹⁰⁴ NOVA Sub-mm Instrumentation Group, Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
¹⁰⁵ Department of Astronomy, School of Physics, Peking University, Beijing 100871, People’s Republic of China
¹⁰⁶ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, People’s Republic of China
¹⁰⁷ Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁰⁸ The Institute of Statistical Mathematics, 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
¹⁰⁹ Department of Statistical Science, The Graduate University for Advanced Studies (SOKENDAI), 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
¹¹⁰ Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8583, Japan
¹¹¹ Leiden Observatory, Leiden University, Postbus 2300, 9513 RA, Leiden, The Netherlands
¹¹² ASTRAVEO LLC, PO Box 1668, Gloucester, MA 01931, USA
¹¹³ Applied Materials Inc., 35 Dory Road, Gloucester, MA 01930, USA
¹¹⁴ Joint Institute for VLBI ERIC (JIVE), Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
¹¹⁵ Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
¹¹⁶ Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan
¹¹⁷ Physics Department, National Sun Yat-Sen University, No. 70, Lien-Hai Road, Kaosiung City 80424, Taiwan, R.O.C.
¹¹⁸ School of Astronomy and Space Science, Nanjing University, Nanjing 210023, People’s Republic of China
¹¹⁹ Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Nanjing 210023, People’s Republic of China
¹²⁰ INAF-Istituto di Radioastronomia, Via P. Gobetti 101, I-40129 Bologna, Italy
¹²¹ INAF-Istituto di Radioastronomia & Italian ALMA Regional Centre, Via P. Gobetti 101, I-40129 Bologna, Italy
¹²² Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan, R.O.C
¹²³ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia 58089, Mexico
¹²⁴ Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, Yunnan Province, People’s Republic of China
¹²⁵ Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, People’s Republic of China
¹²⁶ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 650011 Kunming, People’s Republic of China
¹²⁷ Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA
¹²⁸ School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’s Republic of China
¹²⁹ Institut de Radioastronomie Millimétrique (IRAM), Avenida Divina Pastora 7, Local 20, E-18012 Granada, Spain
¹³⁰ National Institute of Technology, Hachinohe College, 16-1 Uwanotai, Tamonoki, Hachinohe City, Aomori 039-1192, Japan
¹³¹ Astronomy Department, Universidad de Concepción, Casilla 160-C, Concepción, Chile; Research Center for Astronomy, Academy of Athens, Soranou Efessiou 4, 115 27 Athens, Greece
¹³² School of Physics, Georgia Institute of Technology, 837 State St NW, Atlanta, GA 30332, USA
¹³³ Department of Astronomy and Space Science, Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Republic of Korea
¹³⁴ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
¹³⁵ Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
¹³⁶ Canadian Institute for Advanced Research, 180 Dundas St West, Toronto, ON M5G 1Z8, Canada
¹³⁷ Department of Physics, National Taiwan Normal University, No. 88, Sec. 4, Tingzhou Rd., Taipei 116, Taiwan, R.O.C.
¹³⁸ Center of Astronomy and Gravitation, National Taiwan Normal University, No. 88, Sec. 4, Tingzhou Road, Taipei 116, Taiwan, R.O.C.
¹³⁹ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, FI-02540 Kylmälä, Finland
¹⁴⁰ Gemini Observatory/NSF’s NOIRLab, 670 N. Aòhōkū Place, Hilo, HI 96720, USA
¹⁴¹ Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt, Germany
¹⁴² School of Mathematics, Trinity College, Dublin 2, Ireland
¹⁴³ Aalto University Department of Electronics and Nanoengineering, PL 15500, FI-00076 Aalto, Finland
¹⁴⁴ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
¹⁴⁵ National Biomedical Imaging Center, Peking University, Beijing 100871, People’s Republic of China
¹⁴⁶ College of Future Technology, Peking University, Beijing 100871, People’s Republic of China
¹⁴⁷ Tokyo Electron Technology Solutions Limited, 52 Matsunagane, Iwayado, Esashi, Oshu, Iwate 023-1101, Japan
¹⁴⁸ Department of Physics and Astronomy, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
¹⁴⁹ Netherlands Organisation for Scientific Research (NWO), Postbus 93138, 2509 AC, Den Haag, The Netherlands
¹⁵⁰ Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan
¹⁵¹ Astronomical Institute, Tohoku University, Sendai 980-8578, Japan
¹⁵² Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
¹⁵³ University of New Mexico, Department of Physics and Astronomy, Albuquerque, NM 87131, USA
¹⁵⁴ Physics Department, Brandeis University, 415 South Street, Waltham, MA 02453, USA
¹⁵⁵ Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Turku, Finland
¹⁵⁶ Radboud Excellence Fellow of Radboud University, Nijmegen, The Netherlands
¹⁵⁷ School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540, USA
¹⁵⁸ School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People’s Republic of China
¹⁵⁹ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
¹⁶⁰ Center for Astronomy and Astrophysics and Department of Physics, Fudan University, Shanghai 200438, People’s Republic of China
¹⁶¹ Astronomy Department, University of Science and Technology of China, Hefei 230026, People’s Republic of China
¹⁶² Department of Physics and Astronomy, Michigan State University, 567 Wilson Rd, East Lansing, MI 48824, USA
¹⁶³ Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa, Italy
¹⁶⁴ California State University, Los Angeles, Department of Physics and Astronomy, Los Angeles, CA 90032, USA
¹⁶⁵ Dipartimento di Fisica “M. Merlin” dell’Università e del Politecnico di Bari, via Amendola 173, I-70126 Bari, Italy
¹⁶⁶ Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari, Italy
¹⁶⁷ W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA
¹⁶⁸ Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino, Italy
¹⁶⁹ Dipartimento di Fisica, Università degli Studi di Torino, I-10125 Torino, Italy
¹⁷⁰ Laboratoire Leprince-Ringuet, CNRS/IN2P3, École polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France
¹⁷¹ INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, Via E. Bassini 15, I-20133 Milano, Italy
¹⁷² Italian Space Agency, Via del Politecnico snc, 00133 Roma, Italy
¹⁷³ Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352, USA
¹⁷⁴ Istituto Nazionale di Fisica Nucleare, Sezione di Roma “Tor Vergata”, I-00133 Roma, Italy
¹⁷⁵ Space Science Data Center – Agenzia Spaziale Italiana, Via del Politecnico, snc, I-00133 Roma, Italy
¹⁷⁶ Dipartimento di Fisica, Università degli Studi di Perugia, I-06123 Perugia, Italy
¹⁷⁷ Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia, Italy
¹⁷⁸ Grupo de Altas Energías, Universidad Complutense de Madrid, E-28040 Madrid, Spain
¹⁷⁹ Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), 44780 Bochum, Germany
¹⁸⁰ Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan
¹⁸¹ Dipartimento di Fisica, Università di Roma “Tor Vergata”, I-00133 Roma, Italy
¹⁸² Université Paris Cité, Université Paris-Saclay, CEA, CNRS, AIM, F-91191 Gif-sur-Yvette, France
¹⁸³ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁸⁴ Department of Physics, KTH Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm, Sweden
¹⁸⁵ The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm, Sweden
¹⁸⁶ NASA Marshall Space Flight Center, Huntsville AL 35812, USA
¹⁸⁷ The Aerospace Corporation, 14745 Lee Rd, Chantilly, VA 20151, USA
¹⁸⁸ Department of Physics and Center for Space Sciences and Technology, University of Maryland Baltimore County, Baltimore, MD 21250, USA
¹⁸⁹ Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan
¹⁹⁰ Vatican Observatory, V-00120 Castel Gandolfo, Vatican City State
¹⁹¹ Department of physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
¹⁹² INAF-Astronomical Observatory of Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
¹⁹³ Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck, Austria
¹⁹⁴ Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
¹⁹⁵ Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
¹⁹⁶ Santa Cruz Institute for Particle Physics Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064, USA
¹⁹⁷ NYCB Real-Time Computing Inc., Lattingtown, NY 11560-1025, USA
¹⁹⁸ Purdue University Northwest, Hammond, IN 46323, USA
¹⁹⁹ Nagoya University, Institute for Space-Earth Environmental Research, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
²⁰⁰ Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
²⁰¹ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Magrans s/n, E-08193 Barcelona, Spain; and Institut d’Estudis Espacials de Catalunya (IEEC), E-08034 Barcelona, Spain
²⁰² Instituci’o Catalana de Recerca i Estudis Avanccats (ICREA), E-08010 Barcelona, Spain
²⁰³ Center for Astrophysics and Cosmology, University of Nova Gorica, Nova Gorica, Slovenia
²⁰⁴ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
²⁰⁵ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
²⁰⁶ Yerevan State University, 1 Alek Manukyan St., Yerevan 0025, Armenia
²⁰⁷ Landessternwarte, Universität Heidelberg, Königstuhl, D-69117 Heidelberg, Germany
²⁰⁸ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
²⁰⁹ Laboratoire Leprince-Ringuet, École Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France
²¹⁰ Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, 15738 Zeuthen, Germany
²¹¹ Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam, Germany
²¹² Université de Paris, CNRS, Astroparticule et Cosmologie, F-75013 Paris, France
²¹³ Department of Physics and Electrical Engineering, Linnaeus University, 351 95 Växjö, Sweden
²¹⁴ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, D-12489 Berlin, Germany
²¹⁵ Laboratoire Univers et Théories, Observatoire de Paris, Université PSL, CNRS, Université Paris Cité, 5 Pl. Jules Janssen, 92190 Meudon, France
²¹⁶ Sorbonne Université, CNRS/IN2P3, Laboratoire de Physique Nucléaire et de Hautes Energies, LPNHE, 4 place Jussieu, 75005 Paris, France
²¹⁷ IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
²¹⁸ University of Oxford, Department of Physics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
²¹⁹ Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics, Nikolaus-Fiebiger-Str. 2, 91058 Erlangen, Germany
²²⁰ Astronomical Observatory, The University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
²²¹ Instytut Fizyki Jdrowej PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
²²² Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, D-22761 Hamburg, Germany
²²³ School of Physics, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, Johannesburg 2050, South Africa
²²⁴ Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, CC 72, Place Eugène Bataillon, F-34095 Montpellier Cedex 5, France
²²⁵ School of Physical Sciences, University of Adelaide, Adelaide 5005, Australia
²²⁶ Aix Marseille Université, CNRS/IN2P3, CPPM, Marseille, France
²²⁷ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
²²⁸ Universität Innsbruck, Institut für Astro- und Teilchenphysik, Technikerstraße 25, 6020 Innsbruck, Austria
²²⁹ Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland
²³⁰ University of Namibia, Department of Physics, Private Bag 13301, Windhoek 10005, Namibia
²³¹ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun, Poland
²³² Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
²³³ Université Bordeaux, CNRS, LP2I Bordeaux, UMR 5797, F-33170 Gradignan, France
²³⁴ University of Southern Denmark, DK-5230 Odense, Denmark
²³⁵ Department of Physics and Astronomy, The University of Leicester, University Road, Leicester LE1 7RH, UK
²³⁶ Department of Physics, Konan University, 8-9-1 Okamoto, Higashinada, Kobe, Hyogo 658-8501, Japan
²³⁷ Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa, Chiba 277-8583, Japan
²³⁸ Japanese MAGIC Group: Institute for Cosmic Ray Research (ICRR), The University of Tokyo, Kashiwa, 277-8582 Chiba, Japan
²³⁹ ETH Zürich, CH-8093 Zürich, Switzerland
²⁴⁰ Università di Siena and INFN Pisa, I-53100 Siena, Italy
²⁴¹ Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), E-08193 Bellaterra, (Barcelona), Spain
²⁴² Universitat de Barcelona, ICCUB, IEEC-UB, E-08028 Barcelona, Spain
²⁴³ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
²⁴⁴ National Institute for Astrophysics (INAF), I-00136 Rome, Italy
²⁴⁵ Università di Udine and INFN Trieste, I-33100 Udine, Italy
²⁴⁶ Max-Planck-Institut für Physik, D-85748 Garching, Germany
²⁴⁷ Università di Padova and INFN, I-35131 Padova, Italy
²⁴⁸ Croatian MAGIC Group: University of Zagreb, Faculty of Electrical Engineering and Computing (FER), 10000 Zagreb, Croatia
²⁴⁹ Centro Brasileiro de Pesquisas Físicas (CBPF), 22290-180, URCA Rio de Janeiro, (RJ), Brazil
²⁵⁰ IPARCOS Institute and EMFTEL Department, Universidad Complutense de Madrid, E-28040 Madrid, Spain
²⁵¹ Instituto de Astrofísica de Canarias and Dpto. de Astrofísica, Universidad de La Laguna, E-38200 La Laguna, Tenerife, Spain
²⁵² University of Lodz, Faculty of Physics and Applied Informatics, Department of Astrophysics, 90-236 Lodz, Poland
²⁵³ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, E-28040 Madrid, Spain
²⁵⁴ Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain
²⁵⁵ Università di Pisa and INFN Pisa, I-56126 Pisa, Italy
²⁵⁶ INFN MAGIC Group: INFN Sezione di Bari and Dipartimento Interateneo di Fisica dell’Università e del Politecnico di Bari, I-70125 Bari, Italy
²⁵⁷ Department for Physics and Technology, University of Bergen, Bergen, Norway
²⁵⁸ INFN MAGIC Group: INFN Sezione di Torino and Università degli Studi di Torino, I-10125 Torino, Italy
²⁵⁹ Croatian MAGIC Group: University of Rijeka, Faculty of Physics, 51000 Rijeka, Croatia
²⁶⁰ Universität Würzburg, D-97074 Würzburg, Germany
²⁶¹ Technische Universität Dortmund, D-44221 Dortmund, Germany
²⁶² Japanese MAGIC Group: Physics Program, Graduate School of Advanced Science and Engineering, Hiroshima University, 739-8526 Hiroshima, Japan
²⁶³ Armenian MAGIC Group: ICRANet-Armenia, 0019 Yerevan, Armenia
²⁶⁴ Croatian MAGIC Group: University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture (FESB), 21000 Split, Croatia
²⁶⁵ Croatian MAGIC Group: Josip Juraj Strossmayer University of Osijek, Department of Physics, 31000 Osijek, Croatia
²⁶⁶ Finnish MAGIC Group: Finnish Centre for Astronomy with ESO, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
²⁶⁷ Japanese MAGIC Group: Department of Physics, Tokai University, Hiratsuka, 259-1292 Kanagawa, Japan
²⁶⁸ University of Geneva, Chemin d’Ecogia 16, CH-1290 Versoix, Switzerland
²⁶⁹ Saha Institute of Nuclear Physics, A CI of Homi Bhabha National Institute, Kolkata, 700064 West Bengal, India
²⁷⁰ Inst. for Nucl. Research and Nucl. Energy, Bulgarian Academy of Sciences, BG-1784 Sofia, Bulgaria
²⁷¹ Japanese MAGIC Group: Department of Physics, Yamagata University, Yamagata 990-8560, Japan
²⁷² Finnish MAGIC Group: Space Physics and Astronomy Research Unit, University of Oulu, FI-90014 Oulu, Finland
²⁷³ Japanese MAGIC Group: Chiba University, ICEHAP, 263-8522 Chiba, Japan
²⁷⁴ Japanese MAGIC Group: Institute for Space-Earth Environmental Research and Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, 464-6801 Nagoya, Japan
²⁷⁵ Japanese MAGIC Group: Department of Physics, Kyoto University, 606-8502 Kyoto, Japan
²⁷⁶ INFN MAGIC Group: INFN Roma Tor Vergata, I-00133 Roma, Italy
²⁷⁷ Japanese MAGIC Group: Department of Physics, Konan University, Kobe, Hyogo 658-8501, Japan
²⁷⁸ Also at International Center for Relativistic Astrophysics (ICRA), Rome, Italy
²⁷⁹ Also at Port d’Informació Científica (PIC), E-08193 Bellaterra, (Barcelona), Spain
²⁸⁰ Also at Department of Physics, University of Oslo, Oslo, Norway
²⁸¹ Max-Planck-Institut für Physik, D-85748 Garching, Germany
²⁸² Also at INAF Padova, I-35122 Padova, Italy
²⁸³ Japanese MAGIC Group: Institute for Cosmic Ray Research (ICRR), The University of Tokyo, Kashiwa, 277-8582 Chiba, Japan
²⁸⁴ CP3-Origins, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
²⁸⁵ Physics Department, Columbia University, New York, NY 10027, USA
²⁸⁶ Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
²⁸⁷ Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112, USA
²⁸⁸ Physics Department, California Polytechnic State University, San Luis Obispo, CA 94307, USA
²⁸⁹ Department of Physics, Washington University, St. Louis, MO 63130, USA
²⁹⁰ Department of Physics, California State University – East Bay, Hayward, CA 94542, USA
²⁹¹ School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
²⁹² Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064, USA
²⁹³ Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242, USA
²⁹⁴ Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
²⁹⁵ Department of Physics and Astronomy, DePauw University, Greencastle, IN 46135-0037, USA
²⁹⁶ School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
²⁹⁷ Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755, USA
²⁹⁸ Department of Physics, University of Maryland, College Park, MD, USA
²⁹⁹ School of Natural Sciences, University of Galway, University Road, Galway H91 TK33, Ireland
³⁰⁰ Physics Department, McGill University, Montreal, QC H3A 2T8, Canada
³⁰¹ Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
³⁰² Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA
³⁰³ Arthur B. McDonald Canadian Astroparticle Physics Research Institute, 64 Bader Lane, Queen’s University, Kingston, ON K7L 3N6, Canada
³⁰⁴ Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany
³⁰⁵ Fakultät für Physik & Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
³⁰⁶ School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
³⁰⁷ Department of Physical Sciences, Munster Technological University, Bishopstown, Cork T12 P928, Ireland
³⁰⁸ Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
³⁰⁹ Department of Physics, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
³¹⁰ Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027, USA
³¹¹ Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487, USA
³¹² NASA GSFC, Greenbelt, MD 20771, USA
³¹³ Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100101, PR China
³¹⁴ Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi 830011, PR China
³¹⁵ Graduate School of Sciences and Technology for Innovation, Yamaguchi University, J-753-8512 Yamaguchi, Japan
³¹⁶ The Research Institute for Time Studies, Yamaguchi University, J-753-0841 Yamaguchi, Japan
³¹⁷ National Astronomical Research Institute of Thailand (NARIT), 260 Moo 4, T. Donkaew, A. Maerim, 50180 Chiangmai, Thailand
³¹⁸ Graduate School of Science, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
³¹⁹ Center for Astronomy, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
³²⁰ Physical Research Laboratory, Ahmedabad, Gujarat 380009, India

^⋆ Project leader and Fermi-LAT corresponding author. For questions concerning Fermi-LAT results contact giacomo.principe@ts.infn.it
^⋆⋆ H.E.S.S. corresponding author. For questions concerning H.E.S.S. results contact hess@hess-experiment.eu
^† VERITAS corresponding author. For questions concerning VERITAS results contact wjin@astro.ucla.edu, jmsantander@ua.edu

Received: 24 April 2024
Accepted: 29 August 2024

Abstract

Context. The nearby elliptical galaxy M87 contains one of only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (EHT). In 2018, more than two dozen multi-wavelength (MWL) facilities (from radio to γ-ray energies) took part in the second M87 EHT campaign.

Aims. The goal of this extensive MWL campaign was to better understand the physics of the accreting black hole M87*, the relationship between the inflow and inner jets, and the high-energy particle acceleration. Understanding the complex astrophysics is also a necessary first step towards performing further tests of general relativity.

Methods. The MWL campaign took place in April 2018, overlapping with the EHT M87* observations. We present a new, contemporaneous spectral energy distribution (SED) ranging from radio to very high-energy (VHE) γ-rays as well as details of the individual observations and light curves. We also conducted phenomenological modelling to investigate the basic source properties.

Results. We present the first VHE γ-ray flare from M87 detected since 2010. The flux above 350 GeV more than doubled within a period of ≈36 hours. We find that the X-ray flux is enhanced by about a factor of two compared to 2017, while the radio and millimetre core fluxes are consistent between 2017 and 2018. We detect evidence for a monotonically increasing jet position angle that corresponds to variations in the bright spot of the EHT image.

Conclusions. Our results show the value of continued MWL monitoring together with precision imaging for addressing the origins of high-energy particle acceleration. While we cannot currently pinpoint the precise location where such acceleration takes place, the new VHE γ-ray flare already presents a challenge to simple one-zone leptonic emission model approaches, and it emphasises the need for combined image and spectral modelling.