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MINUTE-TIMESCALE > 100 MeV gamma-RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI-LAT IN 2015 JUNE
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2016 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 824, no 2, L20Article in journal (Refereed) Published
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Abstract [en]

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.

Place, publisher, year, edition, pages
2016. Vol. 824, no 2, L20
Keyword [en]
galaxies: active, galaxies: jets, gamma rays: galaxies, quasars: individual (3C 279), radiation mechanisms: non-thermal
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Physical Sciences
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URN: urn:nbn:se:kth:diva-189814DOI: 10.3847/2041-8205/824/2/L20ISI: 000378168200004Scopus ID: 2-s2.0-84976367258OAI: oai:DiVA.org:kth-189814DiVA: diva2:949618
Funder
Knut and Alice Wallenberg FoundationSwedish Research CouncilSwedish National Space Board
Note

QC 20160721

Available from: 2016-07-21 Created: 2016-07-15 Last updated: 2016-07-21Bibliographically approved

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