Identification of γ-ray emission from 3C 345 and NRAO 512

Author： Schinzel F. K. Sokolovsky K. V. D’Ammando F. Burnett T. H. Max-Moerbeck W. Cheung C. C. Fegan S. J. Casandjian J. M. Reyes L. C. Villata M. Raiteri C. M. Agudo I. Bravo Calle O. J. A. Carosati D. Casas R. Gómez J. L. Gurwell M. A. Hsiao H. Y. Jorstad S. G. Kimeridze G. Konstantinova T. S. Kopatskaya E. N. Koptelova E. Kurtanidze O. M. Kurtanidze S. O. Larionov V. M. Larionova E. G. Larionova L. V. Marscher A. P. Morozova D. A. Nikolashvili M. G. Roca-Sogorb M. Ros J. A. Sigua L. A. Spiridonova O. Troitsky I. S. Vlasyuk V. V. Lobanov A. P. Zensus J. A.

Publisher： Edp Sciences

E-ISSN： 1432-0746|532|issue|A150-A150

ISSN： 0004-6361

Source： Astronomy & Astrophysics, Vol.532, Iss.issue, 2011-08, pp. : A150-A150

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Abstract

For more than 15 years, since the days of the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma-Ray Observatory (CGRO; 1991−2000), it has remained an open question why the prominent blazar 3C 345 was not reliably detected at γ-ray energies ≥ 20 MeV. Recently a bright γ-ray source (0FGL J1641.4+3939/1FGL J1642.5+3947), potentially associated with 3C 345, was detected by the Large Area Telescope (LAT) on Fermi. Multiwavelength observations from radio bands to X-rays (mainly GASP-WEBT and Swift) of possible counterparts (3C 345, NRAO 512, B3 1640 + 396) were combined with 20 months of Fermi-LAT monitoring data (August 2008 − April 2010) to associate and identify the dominating γ-ray emitting counterpart of 1FGL J1642.5+3947. The source 3C 345 is identified as the main contributor for this γ-ray emitting region. However, after November 2009 (15 months), a significant excess of photons from the nearby quasar NRAO 512 started to contribute and thereafter was detected with increasing γ-ray activity, possibly adding flux to 1FGL J1642.5+3947. For the same time period and during the summer of 2010, an increase of radio, optical and X-ray activity of NRAO 512 was observed. No γ-ray emission from B3 1640 + 396 was detected.