Minute-Timescale >100 MeV gamma-ray variability during the giant outburst of quasar 3C 279 observed by Fermi-LAT in 2015 June

Markus Ackermann , R. Anantua , K. Asano (1) , Luca Baldini , Guido 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. Cavazzuti , C. Cecchi (2) , C. C. Cheung (3) , J. Chiang , G. Chiaro , S. Ciprini , J. Cohen-Tanugi , F. Costanza , S. Cutini , F. D’ammando , F. De Palma , R. Desiante , S. W. Digel (4) , N. Di Lalla (5) , M. Di Mauro (6) , L. Di Venere , P. S. Drell , C. Favuzzi , S. J. Fegan , E. C. Ferrara (7) , Y. Fukazawa , S. Funk (8) , P. Fusco (9) , F. Gargano , D. Gasparrini , N. Giglietto , F. Giordano , M. Giroletti (10) , I. A. Grenier (11, 12) , Lucas Guillemot (13, 14) , S. Guiriec , M. Hayashida , E. Hays , D. Horan (15) , G. Jóhannesson , S. Kensei , D. Kocevski , M. Kuss (16) , G. La Mura (17) , S. Larsson (18) , L. Latronico , J. Li (19) , F. Longo , F. Loparco (20) , B. Lott (21) , M. N. Lovellette , P. Lubrano , G. M. Madejski , J. D. Magill , S. Maldera , A. Manfreda , M. Mayer (22) , M. N. Mazziotta , P. F. Michelson (23) , N. Mirabal , T. Mizuno , M. E. Monzani , A. Morselli , I. V. Moskalenko , K. Nalewajko , M. Negro (24, 25) , E. Nuss (20) , T. Ohsugi , E. Orlando , D. Paneque , J. S. Perkins (26) , M. Pesce-Rollins , F. Piron (20) , G. Pivato , T. A. Porter (27) , G. Principe , R. Rando , M. Razzano , S. Razzaque , A. Reimer , J. D. Scargle , C. Sgrò (28) , M. Sikora , D. Simone (29) , E. J. Siskind , F. Spada , P. Spinelli (30) , L. Stawarz , J. B. Thayer , D. J. Thompson (31) , D. F. Torres , E. Troja , Y. Uchiyama (32) , Y. Yuan (33) , S. Zimmer (34)

1 Division of Biology, Kansas State University
2 Dipartimento di Scienze Biomediche Sperimentali e Cliniche “Mario Serio”
3 NRL - Naval Research Laboratory
4 SLAC - SLAC National Accelerator Laboratory
5 UGC-DAE Consortium for Scientific Research
6 Department of Molecular Medicine
7 GSFC - NASA Goddard Space Flight Center
8 LSHTM - London School of Hygiene and Tropical Medicine
9 INFN, sezione di Bari - Istituto Nazionale di Fisica Nucleare, sezione di Bari
10 INAF - Istituto Nazionale di Astrofisica
11 ENSA Nantes - École nationale supérieure d'architecture de Nantes
12 UPD7 - Université Paris Diderot - Paris 7
13 USN - Unité Scientifique de la Station de Nançay
14 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
15 LLR - Laboratoire Leprince-Ringuet
16 Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
17 DIEE
18 GU - University of Gothenburg
19 ERTIM - Équipe de Recherche en Textes, Informatique, Multilinguisme
20 LUPM - Laboratoire Univers et Particules de Montpellier
21 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
22 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
23 HEPL - Hansen Experimental Physics Lab [Stanford]
24 UNITO - Università degli studi di Torino = University of Turin
25 INFN, Sezione di Torino - Istituto Nazionale di Fisica Nucleare, Sezione di Torino
26 University of Botswana
27 Department of Animal and Avian Sciences
28 CHU Dijon - Centre Hospitalier Universitaire de Dijon - Hôpital François Mitterrand
29 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
30 ENSA-V - École nationale supérieure d'architecture de Versailles
31 Sea Mammal Research Unit
32 Department of Physics [Tokyo]
33 Department of Biostatistics [Houston]
34 LCFC - Laboratoire de Conception Fabrication Commande

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.

Keywords: radiation mechanisms: non-thermal; gamma rays: galaxies; quasars: individual (3C 27; galaxies: jets; galaxies: active

Domains: Sciences of the Universe [physics]

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⟩