MINUTE-TIMESCALE >100 MeV γ-RAY VARIABILITY during the GIANT OUTBURST of QUASAR 3C 279 OBSERVED by FERMI-LAT in 2015 June

M. Ackermann, R. Anantua, K. Asano, L. Baldini, G. Barbiellini, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, E. Bissaldi, R. D. Blandford, E. D. Bloom, R. Bonino, E. Bottacini, P. Bruel, R. Buehler, G. A. Caliandro, R. A. Cameron, M. Caragiulo, P. A. Caraveo, E. CavazzutiC. Cecchi, C. C. Cheung, J. Chiang, G. Chiaro, S. Ciprini, J. Cohen-Tanugi, F. Costanza, S. Cutini, F. D'Ammando, F. De Palma, R. Desiante, S. W. Digel, N. Di Lalla, M. Di Mauro, L. Di Venere, P. S. Drell, C. Favuzzi, S. J. Fegan, E. C. Ferrara, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, I. A. Grenier, L. Guillemot, S. Guiriec, M. Hayashida, E. Hays, D. Horan, G. Jóhannesson, S. Kensei, D. Kocevski, M. Kuss, G. La Mura, S. Larsson, L. Latronico, J. Li, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, J. D. Magill, S. Maldera, A. Manfreda, M. Mayer, M. N. Mazziotta, P. F. Michelson, N. Mirabal, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, K. Nalewajko, M. Negro, E. Nuss, T. Ohsugi, E. Orlando, D. Paneque, J. S. Perkins, M. Pesce-Rollins, F. Piron, G. Pivato, T. A. Porter, G. Principe, R. Rando, M. Razzano, S. Razzaque, A. Reimer, J. D. Scargle, C. Sgr, M. Sikora, D. Simone, E. J. Siskind, F. Spada, P. Spinelli, L. Stawarz, J. B. Thayer, D. J. Thompson, D. F. Torres, E. Troja, Y. Uchiyama, Y. Yuan, S. Zimmer

Research output: Contribution to journalArticlepeer-review

180 Citations (Scopus)

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.

Original languageEnglish
Article numberL20
JournalAstrophysical Journal Letters
Volume824
Issue number2
DOIs
Publication statusPublished - 20 Jun 2016

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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