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Title: Exploring the blazar zone in high-energy flares of FSRQs

The gamma-ray emission offers a powerful diagnostic tool to probe jets and their surroundings in flat-spectrum radio quasars (FSRQs). In particular, sources emitting at high energies (>10 GeV) give us the strongest constraints. This motivates us to start a systematic study of flares with bright emission above 10 GeV, examining archival data of the Fermi-LAT gamma-ray telescope. At the same time, we began to trigger Target of Opportunity observations to the Swift observatory at the occurrence of high-energy flares, obtaining a wide coverage of the spectral energy distributions (SEDs) for several FSRQs during flares. Among others, we investigate the SED of a peculiar flare of 3C 454.3, showing a remarkably hard gamma-ray spectrum, quite different from the brightest flares of this source, and a bright flare of CTA 102. We modeled the SED in the framework of the one-zone leptonic model, using also archival optical spectroscopic data to derive the luminosity of the broad lines and thus estimate the disk luminosity, from which the structural parameters of the FSRQ nucleus can be inferred. The model allowed us to evaluate the magnetic field intensity in the blazar zone and to locate the emitting region of gamma-rays in the particular case inmore » which gamma-ray spectra show neither absorption from the broad-line region (BLR) nor the Klein-Nishina curvature expected in leptonic models assuming the BLR as the source of seed photons for the External Compton scenario. For FSRQs bright above 10 GeV, we were able to identify short periods lasting less than one day characterized by a high rate of high-energy gamma-rays and hard gamma-ray spectra. We discussed the observed spectra and variability timescales in terms of injection and cooling of energetic particles, arguing that these flares could be triggered by magnetic reconnection events or turbulence in the flow.« less
Authors:
;  [1] ;  [2] ;  [3] ; ; ;  [4] ;  [5]
  1. INAF-Istituto di Astrofisica e Planetologia Spaziale, Via Fosso del Cavaliere 100, I-00133 Rome (Italy)
  2. INAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy)
  3. INAF-Osservatorio Astrofisico di Torino, via P. Giuria 1, I-10125 Torino (Italy)
  4. Instituto Nacional de Astrofisica, Optica y Electronica, Mexico, Luis E, Erro 1, Sta. Maria Tonantzintla, Puebla, CP 72840 (Mexico)
  5. Hiroshima Astrophysical Science Center, Hiroshima University 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan)
Publication Date:
OSTI Identifier:
22364985
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; EMISSION; ENERGY SPECTRA; GALAXIES; GAMMA RADIATION; GAMMA SPECTRA; GEV RANGE; LUMINOSITY; MAGNETIC FIELDS; MAGNETIC RECONNECTION; PHOTONS; QUASARS; TELESCOPES; TURBULENCE