Journal
ASTRONOMY & ASTROPHYSICS
Volume 532, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201016145
Keywords
galaxies: active; quasars: individual: 3C 345; gamma rays: galaxies; quasars: individual: NRAO512; quasars: individual: B3 1640+396
Categories
Funding
- International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne
- Russian RFBR foundation [09-02-00092]
- Spanish Ministry of Science and Innovation
- Regional Government of Andalucia [AYA2007-67626-C03-03, P09-FQM-4784]
- Georgian National Science Foundation [GNSF/ST08/4-404]
- NASA [NNX08AV65G, NNX08AV61G, NNX09AT99G]
- National Science Foundation [AST-0907893]
- Smithsonian Institution
- Academia Sinica
- NASA [NNX08AV61G, 90734, 107306, NNX09AT99G] Funding Source: Federal RePORTER
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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 gamma-ray energies >= 20 MeV. Recently a bright gamma-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, NRAO512, B3 1640+396) were combined with 20 months of Fermi-LAT monitoring data (August 2008-April 2010) to associate and identify the dominating gamma-ray emitting counterpart of 1FGL J1642.5+3947. The source 3C 345 is identified as the main contributor for this gamma-ray emitting region. However, after November 2009 (15 months), a significant excess of photons from the nearby quasar NRAO512 started to contribute and thereafter was detected with increasing gamma-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 NRAO512 was observed. No gamma-ray emission from B3 1640+396 was detected.
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