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Title: 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{sup −5} photons cm{sup −2} s{sup −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 ∼10{sup 49} erg s{sup −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, thismore » predicts extremely low magnetization (∼5 × 10{sup −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 {sub e} ∼ 1.6 × 10{sup 6} 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.« less

Authors:
;  [1]; ; ; ; ; ; ;  [2];  [3];  [4];  [5];  [6];  [7]; ;  [8];  [9];  [10];  [11];  [12] more »; « less
  1. Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany)
  2. W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
  3. Institute for Cosmic-Ray Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8582 (Japan)
  4. Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy)
  5. Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy)
  6. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  7. Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy)
  8. Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy)
  9. Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy)
  10. Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France)
  11. INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica, I-20133 Milano (Italy)
  12. Agenzia Spaziale Italiana (ASI) Science Data Center, I-00133 Roma (Italy)
Publication Date:
OSTI Identifier:
22654297
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 824; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ELECTRIC FIELDS; EMISSION; GALAXIES; GAMMA RADIATION; HADRONS; JET MODEL; LUMINOSITY; MAGNETIC FIELDS; MAGNETIZATION; MEV RANGE 100-1000; PHOTONS; QUASARS; SCHWARZSCHILD RADIUS; SPACE VEHICLES; SPECTRA; SYNCHROTRON RADIATION

Citation Formats

Ackermann, M., Buehler, R., Anantua, R., Baldini, L., Blandford, R. D., Bloom, E. D., Bottacini, E., Caliandro, G. A., Cameron, R. A., Asano, K., Barbiellini, G., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Bissaldi, E., Caragiulo, M., Bonino, R., Bruel, P., Caraveo, P. A., Cavazzuti, E., and and others. MINUTE-TIMESCALE >100 MeV γ -RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI -LAT IN 2015 JUNE. United States: N. p., 2016. Web. doi:10.3847/2041-8205/824/2/L20.
Ackermann, M., Buehler, R., Anantua, R., Baldini, L., Blandford, R. D., Bloom, E. D., Bottacini, E., Caliandro, G. A., Cameron, R. A., Asano, K., Barbiellini, G., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Bissaldi, E., Caragiulo, M., Bonino, R., Bruel, P., Caraveo, P. A., Cavazzuti, E., & and others. MINUTE-TIMESCALE >100 MeV γ -RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI -LAT IN 2015 JUNE. United States. doi:10.3847/2041-8205/824/2/L20.
Ackermann, M., Buehler, R., Anantua, R., Baldini, L., Blandford, R. D., Bloom, E. D., Bottacini, E., Caliandro, G. A., Cameron, R. A., Asano, K., Barbiellini, G., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Bissaldi, E., Caragiulo, M., Bonino, R., Bruel, P., Caraveo, P. A., Cavazzuti, E., and and others. 2016. "MINUTE-TIMESCALE >100 MeV γ -RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI -LAT IN 2015 JUNE". United States. doi:10.3847/2041-8205/824/2/L20.
@article{osti_22654297,
title = {MINUTE-TIMESCALE >100 MeV γ -RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI -LAT IN 2015 JUNE},
author = {Ackermann, M. and Buehler, R. and Anantua, R. and Baldini, L. and Blandford, R. D. and Bloom, E. D. and Bottacini, E. and Caliandro, G. A. and Cameron, R. A. and Asano, K. and Barbiellini, G. and Bastieri, D. and Gonzalez, J. Becerra and Bellazzini, R. and Bissaldi, E. and Caragiulo, M. and Bonino, R. and Bruel, P. and Caraveo, P. A. and Cavazzuti, E. and and others},
abstractNote = {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{sup −5} photons cm{sup −2} s{sup −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 ∼10{sup 49} erg s{sup −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{sup −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 {sub e} ∼ 1.6 × 10{sup 6} 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.},
doi = {10.3847/2041-8205/824/2/L20},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 824,
place = {United States},
year = 2016,
month = 6
}
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