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

Abe K, Abe S, Abhir J, Abhishek A, Acciari VA, Aguasca-Cabot A, Agudo I, Aniello T, Ansoldi S, Antonelli LA, Engels AA, Arcaro C, Asano K, Babić A, de Almeida UB, Barrio JA, Barrios-Jiménez L, Batković I, Baxter J, González JB, Bednarek W, Bernardini E, Bernete J, Berti A, Besenrieder J, Bigongiari C, Biland A, Blanch O, Bonnoli G, Bošnjak , Bronzini E, Burelli I, Campoy-Ordaz A, Carosi A, Carosi R, Carretero-Castrillo M, Castro-Tirado AJ, Cerasole D, Ceribella G, Chilingarian A, Cifuentes A, Colombo E, Contreras JL, Cortina J, Covino S, D’Ammando F, D’Amico G, Vela PD, Dazzi F, De Angelis A, De Lotto B, de Menezes R, Delfino M, Delgado J, Mendez CD, Pierro FD, Tria RD, Venere LD, Dinesh A, Prester DD, Donini A, Dorner D, Doro M, Eisenberger L, Elsaesser D, Escudero J, Fariña L, Foffano L, Font L, Fröse S, Fukazawa Y, López RJ, Garczarczyk M, Gasparyan S, Gaug M, Paiva JG, Giglietto N, Giordano F, Gliwny P, Gradetzke T, Grau R, Green D, Green JG, Günther P, Hadasch D, Hahn A, Hassan T, Heckmann L, Llorente JH, Hrupec D, Imazawa R, Israyelyan D, Itokawa T, Martínez IJ, Quiles JJ, Jormanainen J, Kankkunen S, Kayanoki T, Kerszberg D, Khachatryan M, Kluge GW, Kobayashi Y, Konrad J, Kouch PM, Kubo H, Kushida J, Láinez M, Lamastra A, Lindfors E, Lombardi S, Longo F, López-Coto R, López-Moya M, López-Oramas A, Loporchio S, Lorini A, Lulić L, Lyard E, Majumdar P, Makariev M, Maneva G, Manganaro M, Mangano S, Mannheim K, Mariotti M, Martínez M, Maruševec P, Mas-Aguilar A, Mazin D, Menchiari S, Mender S, Miceli D, Miranda JM, Mirzoyan R, González MM, Molina E, Mondal HA, Moralejo A, Nakamori T, Nanci C, Neustroev V, Nickel L, Rosillo MN, Nigro C, Nikolić L, Nilsson K, Nishijima K, Ekoume TN, Noda K, Nozaki S, Okumura A, Paiano S, Paneque D, Paoletti R, Paredes JM, Pavletić L, Peresano M, Persic M, Pihet M, Pirola G, Podobnik F, Moroni PG, Prandini E, Principe G, Rhode W, Ribó M, Rico J, Righi C, Sahakyan N, Saito T, Saturni FG, Schmitz K, Schmuckermaier F, Schubert JL, Sciaccaluga A, Silvestri G, Sitarek J, Sliusar V, Sobczynska D, Stamerra A, Strišković J, Strom D, Strzys M, Suda Y, Tajima H, Takahashi M, Takeishi R, Temnikov P, Terauchi K, Terzić T, Teshima M, Tutone A, Ubach S, van Scherpenberg J, Acosta MV, Ventura S, Verna G, Viale I, Vigliano A, Vigorito CF, Vitale V, Vovk I, Walter R, Wersig F, Will M, Yamamoto T, Bartolini C, Bissaldi E, Garrappa S, Ankara E, Bader N, Feige M, Hümmer F, Kaplan F, Lorey C, Reinhart D, Schoch K, Steineke R, Marchini A, Ramazani VF, Graham MJ, Hovatta T, Kiehlmann S, Readhead AC, Benke P, Eppel F, Hämmerich S, Heßdörfer J, Kadler M, Kirchner D, Gokus A, Paraschos GF, Rösch F, Sinapius J (2025)

Publication Type: Journal article

Publication year: 2025

Journal

Book Volume: 697

Article Number: A172

DOI: 10.1051/0004-6361/202452942

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 × 10¹⁴ δD cm on the size of the emission region responsible for the γ-ray flare, with δD 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.

Authors with CRIS profile

Involved external institutions

Tokai University / 東海大学 (Tōkai Daigaku) Japan (JP) University of Zagreb / Sveučilište u Zagrebu Croatia (HR) Brazilian Center for Physics Research / Centro Brasileiro de Pesquisas Físicas (CBPF) Brazil (BR) University of Tokyo Japan (JP) Universidad Complutense de Madrid (UCM) Spain (ES) Eidgenössische Technische Hochschule Zürich (ETHZ) / Swiss Federal Institute of Technology in Zurich Switzerland (CH) Universidad de La Laguna Spain (ES) University of Padua / Universita degli Studi di Padova Italy (IT) Università degli Studi di Siena (UNISI) / University of Siena Italy (IT) Institut de Fisica d'Altes Energies (IFAE) / The Institute for High Energy Physics Spain (ES) University of Lodz / Uniwersytet Łódzki Poland (PL) Universitat de Barcelona (UB) / University of Barcelona Spain (ES) Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) Spain (ES) Institute of Astrophysics of Andalusia / Instituto de Astrofísica de Andalucía (IAA-CSIC) Spain (ES) Max-Planck-Institut für Physik (Werner-Heisenberg-Institut, MPP) / Max Planck Institute for Physics Germany (DE) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) Italy (IT) University of Udine / Università degli Studi di Udine Italy (IT) Politecnico di Bari Italy (IT) Autonomous University of Barcelona (UAB) / Universitat Autònoma de Barcelona Spain (ES) University of Pisa / Università di Pisa (UniPi) Italy (IT) Yerevan Physics Institute (YerPhI) / Երևանի Ֆիզիկայի Ինստիտուտ Armenia (AM) Sveučilište u Rijeci / University of Rijeka Croatia (HR) University of Bergen / Universitetet i Bergen Norway (NO) University of Geneva / Université de Genève (UNIGE) Switzerland (CH) Homi Bhabha National Institute (HBNI) India (IN) Hiroshima University / 広島大学 Japan (JP) Nagoya University / 名古屋大学 Japan (JP) National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN) Italy (IT) Julius-Maximilians-Universität Würzburg Germany (DE) University of Turin / Università degli Studi di Torino (UNITO) Italy (IT) Weizmann Institute of Science Israel (IL) Josip-Juraj-Strossmayer-Universität Osijek Croatia (HR) Institute for Nuclear Researches and Nuclear Energy (INRNE) / Институт за ядрени изследвания и ядрена енергетика (ИЯИЯЕ) Bulgaria (BG) Hans-Haffner-Sternwarte Hettstadt Germany (DE) Turku University Hospital / Turun yliopistollinen keskussairaala (TYKS) Finland (FI) California Institute of Technology (Caltech) United States (USA) (US) Foundation for Research and Technology-Hellas (FORTH) / Ίδρυμα Τεχνολογίας και Έρευνας Greece (GR) Yamagata University (YU) Japan (JP) Oulun Yliopisto / University of Oulo Finland (FI) Technische Universität Dortmund Germany (DE) Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy Germany (DE) Deutsches Elektronen-Synchrotron DESY Germany (DE) Chiba University / 千葉大学 Japan (JP) International Center for Relativistic Astrophysics Network (ICRANet) Armenia (AM) Kyoto University / 京都大学 Kyōto daigaku Japan (JP) Konan University / 甲南大学 Japan (JP)

How to cite

APA:

Abe, K., Abe, S., Abhir, J., Abhishek, A., Acciari, V.A., Aguasca-Cabot, A.,... Sinapius, J. (2025). Very high-energy gamma-ray detection and long-term multiwavelength view of the flaring blazar B2 1811+31. Astronomy & Astrophysics, 697. https://doi.org/10.1051/0004-6361/202452942

MLA:

Abe, K., et al. "Very high-energy gamma-ray detection and long-term multiwavelength view of the flaring blazar B2 1811+31." Astronomy & Astrophysics 697 (2025).

BibTeX: Download