Identification of γ-ray emission from 3C 345 and NRAO 512
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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 2011
- DOI:
- 10.1051/0004-6361/201016145
- arXiv:
- arXiv:1107.2926
- Bibcode:
- 2011A&A...532A.150S
- Keywords:
-
- galaxies: active;
- quasars: individual: 3C 345;
- gamma rays: galaxies;
- quasars: individual: NRAO 512;
- quasars: individual: B3 1640+396;
- Astrophysics - Cosmology and Extragalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 11 pages, 5 figures, 5 tables, accepted for publication in A&