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Title: GAMMA-RAY FLARING ACTIVITY FROM THE GRAVITATIONALLY LENSED BLAZAR PKS 1830–211 OBSERVED BY Fermi LAT

The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope routinely detects the MeV-peaked flat-spectrum radio quasar PKS 1830–211 (z = 2.507). Its apparent isotropic γ-ray luminosity (E > 100 MeV), averaged over ∼3 years of observations and peaking on 2010 October 14/15 at 2.9 × 10{sup 50} erg s{sup –1}, makes it among the brightest high-redshift Fermi blazars. No published model with a single lens can account for all of the observed characteristics of this complex system. Based on radio observations, one expects time-delayed variability to follow about 25 days after a primary flare, with flux about a factor of 1.5 less. Two large γ-ray flares of PKS 1830–211 have been detected by the LAT in the considered period, and no substantial evidence for such a delayed activity was found. This allows us to place a lower limit of about 6 on the γ-ray flux ratio between the two lensed images. Swift XRT observations from a dedicated Target of Opportunity program indicate a hard spectrum with no significant correlation of X-ray flux with the γ-ray variability. The spectral energy distribution can be modeled with inverse Compton scattering of thermal photons from the dusty torus. The implications of the LATmore » data in terms of variability, the lack of evident delayed flare events, and different radio and γ-ray flux ratios are discussed. Microlensing effects, absorption, size and location of the emitting regions, the complex mass distribution of the system, an energy-dependent inner structure of the source, and flux suppression by the lens galaxy for one image path may be considered as hypotheses for understanding our results.« less
Authors:
 [1] ; ;  [2] ;  [3] ; ; ; ; ; ;  [4] ;  [5] ; ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10] ;  [11] ;  [12] more »; « less
  1. Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States)
  2. Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany)
  3. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States)
  4. W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
  5. Kavli Institute for Cosmology and Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  6. Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy)
  7. Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy)
  8. Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy)
  9. Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy)
  10. Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, Montpellier (France)
  11. Dipartimento di Fisica "M. Merlin" dell'Università e del Politecnico di Bari, I-70126 Bari (Italy)
  12. Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22364379
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 799; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPTON EFFECT; CORRELATIONS; ENERGY DEPENDENCE; ENERGY SPECTRA; GALAXIES; GAMMA RADIATION; GRAVITATIONAL LENSES; LUMINOSITY; MASS DISTRIBUTION; MEV RANGE; PHOTONS; QUASARS; RED SHIFT; STELLAR FLARES; TELESCOPES; TIME DELAY; X RADIATION