A long-term multiwavelength study of the flat spectrum radio quasar OP 313
: Bartolini, C.; Lindfors, E.; Tramacere, A.; Giroletti, M.; Cerasole, D.; Agudo, I.; Angelakis, E.; Bissaldi, E.; Casaburo, F.; D'ammando, F.; Di Venere, L.; Fallah Ramazani, V.; Giacchino, F.; Giordano, F.; Gurwell, M.; Jormanainen, J.; Jorstad, S.; Keating, G.; Kouch, P. M.; Kraus, A.; Lahteenmaki, A.; Loporchio, S.; Marchili, N.; Marscher, A.; Myserlis, I.; Rao, R.; Righini, S.; Tornikoski, M.
Publisher: EDP Sciences
: 2026
Astronomy and Astrophysics
: A136
: 707
: 0004-6361
: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202556612
: https://doi.org/10.1051/0004-6361/202556612
: https://research.utu.fi/converis/portal/detail/Publication/523409998
Context. The flat spectrum radio quasar OP 313, is a high-redshift (z = 0.997) blazar that entered an intense γ-ray active phase from November 2023 to March 2024, as observed by the as observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope.
Aims. We present a multiwavelength analysis covering 15 years of data, from August 2008 to March 2024, to contextualize this period of extreme γ-ray activity within the long-term emission of the source.
Methods. We analyzed a long-term, comprehensive, multiwavelength dataset from different facilities and projects from radio to γ rays. We identified the seven most intense γ-ray flaring periods and performed a kinematic analysis of Very Long Baseline Array (VLBA) data to determine whether new jet components emerged before or during these flares. For two of these flaring periods, we performed the modeling of the spectral energy distribution (SED).
Results. The VLBA-BU-BLAZAR and MOJAVE datasets reveal a new jet component appearing in both visibility datasets prior to the onset of one of the strongest γ-ray flares. By comparing the timing of the VLBA-BU-BLAZAR knots’ ejection with the γ-ray flaring periods, we constrained the setup of the SED modeling. We also found that the first γ-ray flaring period is less Compton-dominated than the others.
Conclusions. Our results suggest that the recent activity of OP 313, is triggered by new jet components emerging from the core and interacting with a standing shock. The γ-ray emission likely arises from dusty torus photons upscattered via inverse Compton (IC) by relativistic jet electrons. The SED modeling indicates that this component is less dominant during the first γ-ray flaring period than the later ones.
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Author Contributions. C. Bartolini: project leadership, Fermi-LAT data analysis, Swift data analysis, VLBA data analysis, theoretical modeling, paper drafting and editing; E. Lindfors: optical data analysis, interpretation, and paper editing; D. Cerasole: Swift data analysis, optical and γ-ray correlation study, paper editing; A. Tramacere: theoretical modeling and paper drafting; A. Lähteenmäki and M. Tornikoski: Metsähovi data analysis. The rest of the authors have contributed in one or several of the following ways: data acquisition, processing, calibration, and/or reduction; cross-check of the data analysis; draft editing. C.B.: This paper and related research have been conducted during and with the support of the Italian national inter-university PhD program in Space Science and Technology. C.B.: Thanks to Beyoncè’s songs for giving her the necessary strength to write this paper during a difficult time. F.G.: acknowledges financial support from Junta de Castilla y León project SA101P24. J.J.: was supported by Academy of Finland projects 320085 and 345899 P.K.: was supported by Academy of Finland projects 346071 and 345899. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. This work performed in part under DOE Contract DE-AC02-76SF00515. This research has made use of the NASA/IPAC Infrared Science Archive, which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University in Finland. This publication makes use of data based on observations with the 100 m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie). I.M., I.N. and V.K. were funded by the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2018). This study makes use of VLBA data from the VLBA-BU Blazar Monitoring Program (BEAM-ME and VLBA-BU-BLAZAR; http://www.bu.edu/blazars/BEAM-ME.html), funded by NASA through the Fermi Guest Investigator Program. The VLBA is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated by Associated Universities, Inc. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2018). Partly based on observations with the 100-m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at Effelsberg. Observations with the 100-m radio telescope at Effelsberg have received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004719 (ORP). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Maunakea, the location of the SMA, is a culturally important site for the indigenous Hawaiian people; we are privileged to study the cosmos from its summit. This work has made use of data from the Joan Oró Telescope (TJO) of the Montsec Observatory (OdM), which is owned by the Catalan Government and operated by the Institute for Space Studies of Catalonia (IEEC). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW. The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: M.J. Graham). This work has made use of data from the Asteroid Terrestrialimpact Last Alert System (ATLAS) project. The Asteroid Terrestrial-impact Last Alert System (ATLAS) project is primarily funded to search for near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO smarch include images and catalogs from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen’s University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile.
