Very high-energy gamma-ray detection and long-term multiwavelength view of the flaring blazar B2 1811+31

Context. Among the blazars whose emission has been detected up to very high-energy (VHE; 100 GeV< E <100 TeV) γ rays, intermediate synchrotron-peaked BL Lacs (IBLs) are quite rare. The IBL B2 1811+31 ( z = 0.117) exhibited intense flaring activity in 2020. Detailed characterization of the source emission from radio to γ -ray energies was achieved with quasi-simultaneous observations, which led to the first-time detection of VHE γ -ray emission from the source with the MAGIC telescopes. Aims. In this work, we present a comprehensive multiwavelength (MWL) view of B2 1811+31, with a specific focus on the 2020 VHE flare, employing data from MAGIC, Fermi -LAT, Swift -XRT, Swift -UVOT, and several optical and radio ground-based telescopes. Methods. Long-term MWL data were employed to contextualize the high-state episode within the source emissions over 18 years. We investigated the variability, cross-correlations, and classification of the source emissions during low and high states. We propose an interpretative leptonic model for the observed radiative high state. Results. During the 2020 flaring state, the synchrotron peak frequency shifted to higher values and reached the limit of the IBL classification. Variability in timescales of a few hours in the high-energy (HE; 100 MeV< E <100 GeV) γ -ray band poses an upper limit of 6×10 14 δ D cm on the size of the emission region responsible for the γ -ray flare, with δ D being the relativistic Doppler factor of the region. During the 2020 high state, the average spectrum became harder in the HE γ -ray band compared to the low states. A similar behavior has been observed in X-rays. Conversely, during different activity periods, we find harder-when-brighter trends in X-rays and a hint of softer-when-brighter trends at HE γ rays. A long-term HE γ -ray and optical correlation indicates that the same emission regions dominate the radiative output in both ranges, whereas the evolution at 15 GHz shows no correlation with the fluxes at higher frequencies. We test one-zone and two-zone synchrotron-self-Compton models for describing the broadband spectral energy distribution during the 2020 flaring state and investigate the self-consistency of the proposed scenario.

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Journal
Astronomy and Astrophysics
Published
2025-03-27
DOI
https://doi.org/10.1051/0004-6361/202452942
Citations
1
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
Field-Weighted Citation Impact
1.87

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Very high-energy gamma-ray detection and long-term multiwavelength view of the flaring blazar B2 1811+31

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1 citations
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Astrophysics and Cosmic Phenomena
1.87
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Very high-energy gamma-ray detection and long-term multiwavelength view of the flaring blazar B2 1811+31

Patrick Günther, J. Sinapius, J. Sitarek, S. Ventura, D. Sobczyńska, M. Delfino, F. Schmuckermaier, Alessandro Marchini, V. Vitale, T. Nakamori, T. Njoh Ekoume, T. Aniello, S. Mender, E. Bissaldi, Y. Kobayashi, E. Molina, Ž. Bošnjak, Francesco Gabriele Saturni, M. Martı́nez, Alvaro Mas-Aguilar, Cosimo Nigro, C. Bigongiari, D. Hadasch, J.L Schubert, M. Mariotti, Ivana Batković, Florian Eppel, C. Delgado Mendez, Jarred Gershon Green, M. Strzys, S. Paiano, Kenta Terauchi, J. Abhir, Laura Eisenberger, F. Di Pierro, S. Mangano, D. Kerszberg, R. Carosi, J. Baxter, U. Barres de Almeida, Pouya M. Kouch, E. Bernardini, A. López-Oramas, F. Podobnik, R. Paoletti, M. Gaug, D. Cerasole, R. Grau, J. A. Barrio, R. Walter, Stefan Fröse, A. De Angelis, A. Lamastra, K. Nishijima, P. Maruševec, Giacomo D’Amico, E. Colombo, M. Carretero-Castrillo, A. Donini, I. Vovk, L. Font, M. Ribó, C. Vigorito, T. Kayanoki, E. Prandini, J. M. Paredes, Antonio Tutone, V. A. Acciari, G. Verna, Lovro Pavletić, Ryuji Takeishi, N. Sahakyan, P. Majumdar, Takashi Itokawa, A. Berti, D. Mazin, M. Nievas Rosillo, Andrea Gokus, J. Kushida, Martin Will, R. Steineke, S. Kiehlmann, V. Neustroev, D. Israyelyan, H. Kubo, M. Garczarczyk, J. Delgado, K. Nilsson, R. Mirzoyan, C. Lorey, I. Burelli, Y. Fukazawa, A. Lorini, Kai Schmitz, S. Garrappa, G. Bonnoli, L. Foffano, A. Stamerra, P. Benke, D. L. Kirchner, H. A. Mondal, C. Nanci, Niels Bader, D. Dominis Prester, P. Temnikov, M. Kadler, Miguel J. A. Láinez, K. Noda, A. Chilingarian, S. Lombardi, Raniere de Menezes, S. Menchiari, Janusz Konrad, Erno Lindfors, J. Escudero, Gabriella Silvestri, G. Maneva, J. Cortina, T. Hassan, W. Rhode, F. D’Ammando, S. Covino, Arnau Aguasca-Cabot, A. Hahn, Georgios Filippos Paraschos, Gert Werner Kluge, D. Elsäesser, A. C. S. Readhead, V. Fallah Ramazanı, W. Bednarek, P. Gliwny, G. Pirola, N. Giglietto, V. Sliusar, M. Manganaro, S. Gasparyan, J. G. Giesbrecht Paiva, A. Sciaccaluga, A. Cifuentes, L. Heckmann, M. Takahashi, Irene Jiménez Martínez, J. M. Miranda, A. Okumura, E. Lyard, M. Persic, Alessandro Vigliano, A. Carosi, Chiara Righi, J. Besenrieder, M. Pihet, David Reinhart, M. Feige, M. Peresano, L. A. Antonelli, T. Hovatta, R. Imazawa, Frédé́ric Kaplan, M. Khachatryan, J. Bernete, E. Bronzini, A. Campoy-Ordaz, T. Gradetzke, S. Kankkunen, F. Longo, J. Becerra González, Y. Suda, Ana Babić, Marcos López, S. Nozaki, J. Jiménez Quiles, A.J. Castro-Tirado, Matthew J. Graham, R. López-Coto, M. Teshima, M. Doro, R. J. Garcı́a López, A. Abhishek, H. Tajima, R. Di Tria, M. Makariev, J. Herrera Llorente, A. Biland, P. Da Vela, T. Saito, T. Yamamoto, C. Arcaro, M. Vazquez Acosta, Karl Mannheim, J. Strišković, D. Dorner, G. Ceribella, J. Rico, D. Paneque, B. De Lotto, A. Moralejo, K. Asano, G. Principe, M. Molero Gonzalez, D. Strom, F. Dazzi, D. Green, I. Agudo, L. Di Venere, S. Abe, A. Arbet Engels, S. Ubach, S. Ansoldi, J. Jormanainen, T. Terzic, J. van Scherpenberg, I. Viale, S. Loporchio, D. Miceli, J. Heßdörfer, L. Nickel, F. Giordano, P.G. Prada Moroni, F. Rösch, Luis Fariña, O. Blanch, K. Abe, C. Bartolini, K.F. Schoch, D. Hrupec, A. Dinesh, J.L. Contreras, L. Barrios-Jiménez, F. Wersig, L. Nikolić, L. Lulić, E. Ankara, F. Hümmer, S. Hammeric
article en
1 citations

Abstract

Context. Among the blazars whose emission has been detected up to very high-energy (VHE; 100 GeV< E <100 TeV) γ rays, intermediate synchrotron-peaked BL Lacs (IBLs) are quite rare. The IBL B2 1811+31 ( z = 0.117) exhibited intense flaring activity in 2020. Detailed characterization of the source emission from radio to γ -ray energies was achieved with quasi-simultaneous observations, which led to the first-time detection of VHE γ -ray emission from the source with the MAGIC telescopes. Aims. In this work, we present a comprehensive multiwavelength (MWL) view of B2 1811+31, with a specific focus on the 2020 VHE flare, employing data from MAGIC, Fermi -LAT, Swift -XRT, Swift -UVOT, and several optical and radio ground-based telescopes. Methods. Long-term MWL data were employed to contextualize the high-state episode within the source emissions over 18 years. We investigated the variability, cross-correlations, and classification of the source emissions during low and high states. We propose an interpretative leptonic model for the observed radiative high state. Results. During the 2020 flaring state, the synchrotron peak frequency shifted to higher values and reached the limit of the IBL classification. Variability in timescales of a few hours in the high-energy (HE; 100 MeV< E <100 GeV) γ -ray band poses an upper limit of 6×10 14 δ D cm on the size of the emission region responsible for the γ -ray flare, with δ D being the relativistic Doppler factor of the region. During the 2020 high state, the average spectrum became harder in the HE γ -ray band compared to the low states. A similar behavior has been observed in X-rays. Conversely, during different activity periods, we find harder-when-brighter trends in X-rays and a hint of softer-when-brighter trends at HE γ rays. A long-term HE γ -ray and optical correlation indicates that the same emission regions dominate the radiative output in both ranges, whereas the evolution at 15 GHz shows no correlation with the fluxes at higher frequencies. We test one-zone and two-zone synchrotron-self-Compton models for describing the broadband spectral energy distribution during the 2020 flaring state and investigate the self-consistency of the proposed scenario.

Astronomy and AstrophysicsVol. 697
University of Siena (IT), University of Pisa (IT), Yamagata University (JP), Hiroshima University (JP), University of Geneva (CH), Obayashi (Japan) (JP), Universidad Complutense de Madrid (ES), California Institute of Technology (US), Universitat Autònoma de Barcelona (ES), University of Udine (IT), Centre National de la Recherche Scientifique (FR), Tokai University (JP), A. Alikhanyan National Laboratory (AM), University of Padua (IT), University of Trieste (IT), University of Rijeka (HR), University of Turku (FI), Universidad de La Laguna (ES), Chiba University (JP), Konan University (JP), Saha Institute of Nuclear Physics (IN), University of Zagreb (HR), Friedrich-Alexander-Universität Erlangen-Nürnberg (DE), Turku Centre for Computer Science (FI), University of Oslo (NO), Institute for High Energy Physics (ES), University of Trento (IT), Homi Bhabha National Institute (IN), TU Dortmund University (DE), Washington University in St. Louis (US), Université Paris Cité (FR), Kyoto University (JP), Bulgarian Academy of Sciences (BG), University of Würzburg (DE), Deutsches Elektronen-Synchrotron DESY (DE), Laboratoire AstroParticule et Cosmologie (FR), University of Łódź (PL), ETH Zurich (CH), Max Planck Institute for Physics (DE), Istituto Nazionale di Fisica Nucleare, Sezione di Torino (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Bari (IT), Istituto di Radioastronomia di Bologna (IT), Finnish Youth Research Society (FI), International Center for Relativistic Astrophysics (IT), Centro Brasileiro de Pesquisas Físicas (BR), Instituto de Astrofísica de Canarias (ES), MVZ Labor Ravensburg (DE), International Center for Relativistic Astrophysics Network (AM), Port d'Informació Científica (ES), Istituto Nazionale di Fisica Nucleare, Sezione di Roma I (IT), Max Planck Institute for Radio Astronomy (DE), Instituto de Astrofísica de Andalucía (ES), Osservatorio Astronomico di Padova (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (ES), University of Bergen (NO), University of Osijek (HR), Weizmann Institute of Science (IL), University of Turin (IT), Nagoya University (JP), Polytechnic University of Bari (IT), Universitat de Barcelona (ES), The University of Tokyo (JP), National Institute for Astrophysics (IT), Foundation for Research and Technology Hellas (GR), University of Oulu (FI), Aalto University (FI)
National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, California Institute of Technology, Centres de Recerca de Catalunya, European Commission, Deutsche Forschungsgemeinschaft, Ministry of Education, Culture, Sports, Science and Technology, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Bundesministerium für Bildung und Forschung, Generalitat de Catalunya, Centre National d’Etudes Spatiales, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Max-Planck-Gesellschaft, Vetenskapsrådet, Hrvatska Zaklada za Znanost, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Centre National de la Recherche Scientifique, Ministério da Ciência, Tecnologia, Inovações e Comunicações, Instituto de Astrofísica de Canarias, Japan Society for the Promotion of Science, Japan Aerospace Exploration Agency, European Regional Development Fund, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules, Institute for Cosmic Ray Research, University of Tokyo, Integrated Electronics Engineering Center, Binghamton University
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