MINUTE-TIMESCALE >100 MeV γ-RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI-LAT IN 2015 JUNE

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 obse...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2016-06, Vol.824 (2), p.L20-L20
Main Authors: Ackermann, M., Asano, K., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Bruel, P., Buehler, R., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cecchi, C., Cheung, C. C., Chiang, J., Chiaro, G., Ciprini, S., Cohen-Tanugi, J., Costanza, F., Cutini, S., D'Ammando, F., Palma, F. de, Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Drell, P. S., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Fukazawa, Y., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Grenier, I. A., Guillemot, L., Guiriec, S., Hayashida, M., Hays, E., Horan, D., Jóhannesson, G., Kensei, S., Kocevski, D., Kuss, M., Mura, G. La, Larsson, S., Latronico, L., Li, J., Longo, F., Loparco, F., Lott, B., Lubrano, P., Madejski, G. M., Magill, J. D., Maldera, S., Manfreda, A., Mayer, M., Mazziotta, M. N., Michelson, P. F., Mirabal, N., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Nalewajko, K., Negro, M., Nuss, E., Ohsugi, T., Orlando, E., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Pivato, G., Porter, T. A., Principe, G., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Scargle, J. D., Sgrò, C., Sikora, M., Simone, D., Siskind, E. J., Spada, F., Spinelli, P., Stawarz, L., Thayer, J. B., Thompson, D. J., Torres, D. F., Troja, E., Uchiyama, Y., Zimmer, S.
Format: Article
Language:English
Subjects:
ABSORPTION
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ELECTRIC FIELDS
EMISSION
Flux
GALAXIES
galaxies: active
galaxies: jets
GAMMA RADIATION
gamma rays: galaxies
HADRONS
JET MODEL
Lorentz factor
LUMINOSITY
MAGNETIC FIELDS
MAGNETIZATION
MEV RANGE 100-1000
Orbits
Outbursts
PHOTONS
QUASARS
quasars: individual (3C 279)
radiation mechanisms: non-thermal
SCHWARZSCHILD RADIUS
SPACE VEHICLES
SPECTRA
SYNCHROTRON RADIATION
Time
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Summary: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 γe ∼ 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.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8205/824/2/L20