Minute-timescale >100 MeV γ-Ray Variability during the Giant Outburst of Quasar 3C 279 Observed by Fermi-LAT in 2015 June
Journal
Date Issued
2016
Author(s)
Ackermann, M.
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Anantua, R.
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Asano, K.
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Baldini, L.
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Barbiellini, G.
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Bastieri, D.
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Becerra Gonzalez, J.
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Bellazzini, R.
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Bissaldi, E.
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Blandford, R. D.
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Bloom, E. D.
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Orlando, E.
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Paneque, D.
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Perkins, J. S.
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Pesce-Rollins, M.
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Piron, F.
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Pivato, G.
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Porter, T. A.
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Rando, R.
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Razzano, M.
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Razzaque, S.
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Reimer, A.
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Scargle, J. D.
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Sgrò, C.
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Sikora, M.
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Simone, D.
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Siskind, E. J.
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Spada, F.
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Spinelli, P.
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Stawarz, L.
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Thayer, J. B.
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Thompson, D. J.
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Torres, D. F.
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Troja, E.
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Uchiyama, Y.
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Yuan, Y.
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Zimmer, S.
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Bonino, R.
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Bottacini, E.
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Bruel, P.
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Buehler, R.
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Caliandro, G. A.
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Cameron, R. A.
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Caragiulo, M.
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Cavazzuti, E.
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Cecchi, C.
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Cheung, C. C.
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Chiang, J.
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Chiaro, G.
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Ciprini, S.
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Cohen-Tanugi, J.
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Costanza, F.
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Cutini, S.
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de Palma, F.
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Desiante, R.
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Digel, S. W.
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Di Lalla, N.
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Di Mauro, M.
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Di Venere, L.
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Drell, P. S.
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Favuzzi, C.
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Fegan, S. J.
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Ferrara, E. C.
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Fukazawa, Y.
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Funk, S.
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Fusco, P.
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Gargano, F.
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Gasparrini, D.
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Giglietto, N.
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Giordano, F.
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Grenier, I. A.
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Guillemot, L.
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Guiriec, S.
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Hayashida, M.
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Hays, E.
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Horan, D.
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Jóhannesson, G.
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Kensei, S.
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Kocevski, D.
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Kuss, M.
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Larsson, S.
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Latronico, L.
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Li, J.
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Longo, F.
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Loparco, F.
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Lott, B.
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Lovellette, M. N.
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Lubrano, P.
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Madejski, G. M.
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Magill, J. D.
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Maldera, S.
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Manfreda, A.
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Mayer, M.
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Mazziotta, M. N.
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Michelson, P. F.
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Mirabal, N.
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Mizuno, T.
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Monzani, M. E.
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Morselli, A.
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Moskalenko, I. V.
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Nalewajko, K.
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Negro, M.
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Nuss, E.
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Ohsugi, T.
Abstract
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 ∼3.6 × 10-5 photons cm-2 s-1, averaged over orbital period intervals. It is historically the highest γ-ray flux observed from the source, including past EGRET observations, with the γ-ray isotropic luminosity reaching ∼1049 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 (Γ) of 35 is necessary to avoid both internal γ-ray absorption and super-Eddington jet power. In the standard external radiation Comptonization scenario, Γ should be at least 50 to avoid overproducing the synchrotron self-Compton component. However, this predicts extremely low magnetization (∼5 × 10-4). Equipartition requires Γ as high as 120, unless the emitting region is a small fraction of the dissipation region. Alternatively, we consider γ rays originating as synchrotron radiation of γ e ∼ 1.6 × 106 electrons, in a magnetic field B ∼ 1.3 kG, accelerated by strong electric fields E ∼ B in the process of magnetoluminescence. At such short distance scales, one cannot immediately exclude the production of γ-rays in hadronic processes.
Volume
824
Issue
2
Start page
L20
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...824L..20A
Rights
open.access
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