Multiwavelength study of OT 081: broadband modelling of a transitional blazar

ABSTRACT OT 081 is a well-known, luminous blazar that is remarkably variable in many energy bands. We present the first broadband study of the source, which includes very high energy (VHE, $E\gt $ 100 GeV) $\gamma$-ray data taken by the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov telescopes) and H.E.S.S. (High Energy Stereoscopic System) imaging Cherenkov telescopes. The discovery of VHE $\gamma$-ray emission happened during a high state of $\gamma$-ray activity in July 2016, observed by many instruments from radio to VHE $\gamma$-rays. We identify four states of activity of the source, one of which includes VHE $\gamma$-ray emission. Variability in the VHE domain is found on daily time-scales. The intrinsic VHE spectrum can be described by a power law with index $3.27\pm 0.44_{\rm stat}\pm 0.15_{\rm sys}$ (MAGIC) and $3.39\pm 0.58_{\rm stat}\pm 0.64_{\rm sys}$ (H.E.S.S.) in the energy range of 55–300 and 120–500 GeV, respectively. The broadband emission cannot be successfully reproduced by a simple one-zone synchrotron self-Compton model. Instead, an additional external Compton component is required. We test a lepto-hadronic model that reproduces the data set well and a proton-synchrotron-dominated model that requires an extreme proton luminosity. Emission models that are able to successfully represent the data place the emitting region well outside of the broad-line region to a location at which the radiative environment is dominated by the infrared thermal radiation field of the dusty torus. In the scenario described by this flaring activity, the source appears to be a flat spectrum radio quasar (FSRQ), in contrast with past categorizations. This suggests that the source can be considered to be a transitional blazar, intermediate between BL Lac and FSRQ objects.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-12-30
DOI
https://doi.org/10.1093/mnras/stae2469
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1
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Astrophysics and Cosmic Phenomena
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article
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0.66

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Multiwavelength study of OT 081: broadband modelling of a transitional blazar

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1 citations
Monthly Notices of the Royal Astronomical Society
Astrophysics and Cosmic Phenomena
0.66
article

Multiwavelength study of OT 081: broadband modelling of a transitional blazar

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article en
1 citations

Abstract

ABSTRACT OT 081 is a well-known, luminous blazar that is remarkably variable in many energy bands. We present the first broadband study of the source, which includes very high energy (VHE, $E\gt $ 100 GeV) $\gamma$-ray data taken by the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov telescopes) and H.E.S.S. (High Energy Stereoscopic System) imaging Cherenkov telescopes. The discovery of VHE $\gamma$-ray emission happened during a high state of $\gamma$-ray activity in July 2016, observed by many instruments from radio to VHE $\gamma$-rays. We identify four states of activity of the source, one of which includes VHE $\gamma$-ray emission. Variability in the VHE domain is found on daily time-scales. The intrinsic VHE spectrum can be described by a power law with index $3.27\pm 0.44_{\rm stat}\pm 0.15_{\rm sys}$ (MAGIC) and $3.39\pm 0.58_{\rm stat}\pm 0.64_{\rm sys}$ (H.E.S.S.) in the energy range of 55–300 and 120–500 GeV, respectively. The broadband emission cannot be successfully reproduced by a simple one-zone synchrotron self-Compton model. Instead, an additional external Compton component is required. We test a lepto-hadronic model that reproduces the data set well and a proton-synchrotron-dominated model that requires an extreme proton luminosity. Emission models that are able to successfully represent the data place the emitting region well outside of the broad-line region to a location at which the radiative environment is dominated by the infrared thermal radiation field of the dusty torus. In the scenario described by this flaring activity, the source appears to be a flat spectrum radio quasar (FSRQ), in contrast with past categorizations. This suggests that the source can be considered to be a transitional blazar, intermediate between BL Lac and FSRQ objects.

Monthly Notices of the Royal Astronomical SocietyVol. 540(1)
University of Siena (IT), University of Pisa (IT), Boston University (US), 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), Jagiellonian University (PL), Centre National de la Recherche Scientifique (FR), Goddard Space Flight Center (US), Tokai University (JP), A. Alikhanyan National Laboratory (AM), University of Padua (IT), University of Trieste (IT), École Polytechnique (FR), University of Crete (GR), Valparaiso University (US), University of Leicester (GB), University of Rijeka (HR), University of Turku (FI), Universidad de La Laguna (ES), Universität Hamburg (DE), Chiba University (JP), Konan University (JP), Saha Institute of Nuclear Physics (IN), University of Concepción (CL), St Petersburg University (RU), University of Potsdam (DE), 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), Universität Innsbruck (AT), Homi Bhabha National Institute (IN), TU Dortmund University (DE), Université Paris Cité (FR), Aix-Marseille Université (FR), University of Namibia (NA), Shanghai Normal University (CN), Linnaeus University (SE), Heidelberg University (DE), University of Würzburg (DE), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), North-West University (ZA), Université Paris-Saclay (FR), Laboratoire d’Annecy de Physique des Particules (FR), Astronomical Observatory of Rome (IT), Agenzia Spaziale Italiana (IT), Laboratoire AstroParticule et Cosmologie (FR), University of Łódź (PL), ETH Zurich (CH), University of Catania (IT), Sorbonne Université (FR), University of Oxford (GB), Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (IT), Chinese Academy of Science South America Center for Astronomy (CL), Max Planck Institute for Physics (DE), Istituto Nazionale di Fisica Nucleare, Sezione di Torino (IT), Institute of Physics (AZ), Universidad de Playa Ancha de Ciencias de la Educación (CL), Laboratoire de Physique Nucléaire et de Hautes Énergies (FR), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (IT), Institute of Nuclear Physics, Polish Academy of Sciences (PL), Istituto Nazionale di Fisica Nucleare, Sezione di Bari (IT), Istituto di Radioastronomia di Bologna (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Catania (IT), Institute for Nuclear Research and Nuclear Energy (BG), Frauenklinik Heidelberg (DE), Finnish Youth Research Society (FI), International Center for Relativistic Astrophysics (IT), Ruđer Bošković Institute (HR), Centro Brasileiro de Pesquisas Físicas (BR), CEA Paris-Saclay (FR), Instituto de Astrofísica de Canarias (ES), Nicolaus Copernicus Astronomical Center (PL), International Center for Relativistic Astrophysics Network (AM), Port d'Informació Científica (ES), Laboratoire Leprince-Ringuet (FR), Astronomical Observatory (RS), Istituto Nazionale di Fisica Nucleare, Sezione di Roma I (IT), Instituto de Astrofísica de Andalucía (ES), Osservatorio Astronomico di Padova (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT), Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (IT), Institut de Recherche sur les Lois Fondamentales de l'Univers (FR), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (ES), Deleted Institution, Institute of Science and Technology, University of Bergen (NO), University of Warsaw (PL), University of Osijek (HR), University of Turin (IT), The University of Adelaide (AU), Nagoya University (JP), Liverpool John Moores University (GB), Polytechnic University of Bari (IT), Université Savoie Mont Blanc (FR), Universitat de Barcelona (ES), The University of Tokyo (JP), University of Valparaíso (CL), University of Tübingen (DE), National Institute for Astrophysics (IT), Foundation for Research and Technology Hellas (GR), University of California, Berkeley (US), University of Oulu (FI), Aalto University (FI)
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