Minute-Timescale >100 MeV gamma-ray variability during the giant outburst of quasar 3C 279 observed by Fermi-LAT in 2015 June - Archive ouverte HAL Access content directly
Journal Articles The Astrophysical journal letters Year : 2016

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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Markus Ackermann
  • Function : Author
R. Anantua
  • Function : Author
K. Asano
Luca Baldini
  • Function : Author
Guido Barbiellini
  • Function : Author
D. Bastieri
  • Function : Author
J. Becerra Gonzalez
  • Function : Author
R. Bellazzini
  • Function : Author
E. Bissaldi
  • Function : Author
R. D. Blandford
  • Function : Author
E. D. Bloom
  • Function : Author
R. Bonino
  • Function : Author
E. Bottacini
  • Function : Author
P. Bruel
R. Buehler
  • Function : Author
G. A. Caliandro
  • Function : Author
R. A. Cameron
  • Function : Author
M. Caragiulo
  • Function : Author
P. A. Caraveo
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E. Cavazzuti
  • Function : Author
J. Chiang
  • Function : Author
G. Chiaro
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S. Ciprini
  • Function : Author
J. Cohen-Tanugi
F. Costanza
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S. Cutini
  • Function : Author
F. D’ammando
F. De Palma
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R. Desiante
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L. Di Venere
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P. S. Drell
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C. Favuzzi
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S. J. Fegan
Y. Fukazawa
F. Gargano
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D. Gasparrini
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N. Giglietto
F. Giordano
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S. Guiriec
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M. Hayashida
  • Function : Author
E. Hays
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G. Jóhannesson
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S. Kensei
  • Function : Author
D. Kocevski
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G. La Mura
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L. Latronico
  • Function : Author
F. Longo
B. Lott
M. N. Lovellette
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P. Lubrano
  • Function : Author
G. M. Madejski
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J. D. Magill
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S. Maldera
  • Function : Author
A. Manfreda
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M. N. Mazziotta
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N. Mirabal
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T. Mizuno
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M. E. Monzani
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A. Morselli
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I. V. Moskalenko
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K. Nalewajko
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T. Ohsugi
  • Function : Author
E. Orlando
  • Function : Author
D. Paneque
M. Pesce-Rollins
G. Pivato
  • Function : Author
G. Principe
  • Function : Author
R. Rando
  • Function : Author
M. Razzano
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S. Razzaque
  • Function : Author
A. Reimer
J. D. Scargle
  • Function : Author
M. Sikora
  • Function : Author
E. J. Siskind
  • Function : Author
F. Spada
  • Function : Author
L. Stawarz
  • Function : Author
J. B. Thayer
  • Function : Author
D. F. Torres
  • Function : Author
E. Troja
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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 $\sim3.6\times10^{-5}\;{\rm photons}\;{\rm cm}^{-2}\;{\rm s}^{-1}$ averaged over orbital period intervals. It is the historically highest $\gamma$-ray flux observed from the source including past EGRET observations, with the $\gamma$-ray isotropic luminosity reaching $\sim10^{49}\;{\rm erg}\;{\rm s}^{-1}$. During the outburst, the Fermi spacecraft, which has an orbital period of 95.4 min, 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-min binned timescales, with flux doubling times less than 5 min. 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, $\Gamma$ should be at least 50 to avoid overproducing the synchrotron-self-Compton component. However, this predicts extremely low magnetization ($\sim5\times10^{-4}$). Equipartition requires $\Gamma$ as high as 120, unless the emitting region is a small fraction of the dissipation region. Alternatively, we consider $\gamma$ rays originating as synchrotron radiation of $\gamma_{\rm e}\sim1.6\times10^6$ electrons, in magnetic field $B\sim1.3$ kG, accelerated by strong electric fields $E\sim B$ in the process of magnetoluminescence. At such short distance scales, one cannot immediately exclude production of $\gamma$ rays in hadronic processes.
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insu-01360099 , version 1 (05-05-2020)

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Markus Ackermann, R. Anantua, K. Asano, Luca Baldini, Guido Barbiellini, et al.. Minute-Timescale >100 MeV gamma-ray variability during the giant outburst of quasar 3C 279 observed by Fermi-LAT in 2015 June: Ammando 24,25 , F. de Palma 12. The Astrophysical journal letters, 2016, 824 (L20), 8 p. ⟨10.3847/2041-8205/824/2/L20⟩. ⟨insu-01360099⟩
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