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.
Identification of gamma-ray emission from 3C 345 and NRAO 512 / Schinzel FK; Sokolovsky KV; DAmmando F; Burnett TH; Max-Moerbeck W; Cheung CC; Fegan SJ; Casandjian JM; Reyes LC; Villata M; Raiteri CM; Agudo I; Calle OJAB; Carosati D; Casas R; Gomez JL; Gurwell MA; Hsiao HY; Jorstad SG; Kimeridze G; Konstantinova TS; Kopatskaya EN; Koptelova E; Kurtanidze OM; Kurtanidze SO; Larionov VM; Larionova EG; Larionova LV; Marscher AP; Morozova DA; Nikolashvili MG; Roca-Sogorb M; Ros JA; Sigua LA; Spiridonova O; Troitsky IS; Vlasyuk VV; Lobanov AP; Zensus JA. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - STAMPA. - 532:(2011), pp. A150.1-A150.11. [10.1051/0004-6361/201016145]
Identification of gamma-ray emission from 3C 345 and NRAO 512
D'AMMANDO, FILIPPO;
2011
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 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
