Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013-2017

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Research units

  • University of Turku
  • California Institute of Technology
  • INAF Istituto di Radioastronomia
  • INAF—Osservatorio Astrofisico di Torino
  • Instituto de Astrofísica de Canarias
  • University of La Laguna
  • Instituto de Astrofisica de Andalucia (Spain)
  • Pulkovo Observatory
  • Bulgarian Academy of Sciences
  • Crimean Astrophysical Observatory
  • Universidad Nacional Autonoma de Mexico
  • Fundación Galileo Galilei
  • Sofia University St. Kliment Ohridski
  • Osservatorio Astronomico della Regione Autonoma Valle d'Aosta
  • EPT Observatories
  • Max-Planck-Institut für Radioastronomie
  • University of Southampton
  • National Central University
  • Astronomical Observatory
  • INAF, Osservatorio Astronomico di Roma
  • Ulugh Beg Astronomical Institute, Maidanak Observatory
  • St. Petersburg State University
  • Harvard-Smithsonian Center for Astrophysics
  • Liverpool John Moores University
  • Dublin Institute for Advanced Studies
  • Boston University
  • Abastumani Observatory
  • Al Farabi Kazakh National University
  • Fesenkov Astrophysical Institute
  • Kazan Federal University
  • Heidelberg University 
  • Guangzhou University
  • Osaka Kyoiku University
  • University College Dublin
  • Brigham Young University
  • Michael Adrian Observatorium
  • Technische Hochschule Mittelhessen (THM) Giessen - University of Applied Sciences Mittelhessen
  • Command Module Observatory
  • Nordic Optical Telescope
  • Osservatorio Astronomico Sirio
  • Observatoire de Paris
  • University of Colorado
  • Lowell Observatory
  • University of Arizona
  • Instituto de Radio Astronomia Milimétrica
  • Universidad de Chile
  • Universidad de Concepción
  • Chinese Academy of Sciences
  • RAS - Special Astrophysical Observatory


We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013-2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (gamma-rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented gamma-ray flaring activity was observed during 2016 November-2017 February, with four major outbursts. A peak flux of (2158 +/- 63) x 10(-8) ph cm(-2) s(-1), corresponding to a luminosity of (2.2 +/- 0.1) x10(50) erg s(-1), was reached on 2016 December 28. These four gamma-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and gamma-ray activity is found. The gamma-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This gamma-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission.


Original languageEnglish
Pages (from-to)5300-5316
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - Dec 2019
MoE publication typeA1 Journal article-refereed

    Research areas

  • radiation mechanisms: non-thermal, galaxies: individual: CTA 102, galaxies: jets, galaxies: nuclei, gamma-rays: general, SWIFT, VARIABILITY, TELESCOPE, BLAZARS, FERMI, OBJECTS, CALIBRATION, RADIATION, FLARES, SCALE

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