Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 824, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/2041-8205/824/2/L20
Keywords
galaxies: active; galaxies: jets; gamma rays: galaxies; quasars: individual (3C 279); radiation mechanisms: non-thermal
Categories
Funding
- NASA (United States)
- DOE (United States)
- CEA/Irfu (France)
- IN2P3/CNRS (France)
- ASI (Italy)
- NFN (Italy)
- MEXT (Japan)
- KEK (Japan)
- JAXA (Japan)
- K.A. Wallenberg Foundation
- Swedish Research Council
- National Space Board (Sweden)
- INAF (Italy)
- CNES (France)
- JSPS KAKENHI [JP15K17640]
- ICREA Funding Source: Custom
- Grants-in-Aid for Scientific Research [16K05291, 15K17640] Funding Source: KAKEN
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On 2015 June 16, Fermi- LAT observed a giant outburst from the flat spectrum radio quasar 3C 279 with a peak >100 MeV flux of similar to 3.6 x 10(-5) photons cm(-2) s(-1), averaged over orbital period intervals. It is historically the highest gamma-ray flux observed from the source, including past EGRET observations, with the gamma-ray isotropic luminosity reaching similar to 10(49) erg s(-1). During the outburst, the Fermi spacecraft, which has an orbital period of 95.4 minutes, was operated in a special pointing mode to optimize the exposure for 3C 279. For the first time, significant flux variability at sub-orbital timescales was found in blazar observations by Fermi- LAT. The source flux variability was resolved down to 2-minute binned timescales, with flux doubling times of less than 5 minutes. The observed minute-scale variability suggests a very compact emission region at hundreds of Schwarzschild radii from the central engine in conical jet models. A minimum bulk jet Lorentz factor (Gamma) of 35 is necessary to avoid both internal gamma-ray absorption and super-Eddington jet power. In the standard external radiation Comptonization scenario, G should be at least 50 to avoid overproducing the synchrotron self-Compton component. However, this predicts extremely low magnetization (similar to 5 x 10(-4)). Equipartition requires Gamma as high as 120, unless the emitting region is a small fraction of the dissipation region. Alternatively, we consider. rays originating as synchrotron radiation of gamma e similar to 1.6 x 10(6) electrons, in a magnetic field B similar to 1.3 kG, accelerated by strong electric fields E similar to B in the process of magnetoluminescence. At such short distance scales, one cannot immediately exclude the production of gamma-rays in hadronic processes.
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