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First minute-scale variability in Fermi -LAT blazar observations during the giant outburst of 3C279 in 2015 June
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2017 (English)In: AIP Conference Proceedings, American Institute of Physics Inc. , 2017Conference paper (Refereed)
Abstract [en]

The Flat Spectrum Radio Quasar 3C 279 underwent several outbursts in the past, having flared with a peak γ-ray flux above 100 MeV (FE>100 MeV) exceeding 10-5 ph cm-2 s-1, in 2013 December, 2014 April, and 2015 June. The 2013 December outburst showed an unusually hard power-law γ-ray spectrum (index∼1.7), and an asymmetric light curve profile with few-hour time scale variability. This could be successfully explained using our second order Fermi acceleration model. The outburst in 2015 June was even more powerful, with FE>100 MeV ∼ 4×10-5 ph cm-2 s-1, the historically highest even when the EGRET era is included. For the first time, significant flux variability at sub-orbital timescales was found in blazar observations by Fermi-LAT, with flux doubling times of less than 5 minutes. In the standard external-Compton scenario with conical jet geometry, the minute-scale variability requires a very high bulk jet Lorentz factor (> 50) and extremely low magnetization even at the jet base (∼ 100RS). However, such a high bulk jet Lorentz factor and low magnetization at the jet base pose challenges to standard models of electromagnetically driven jets. Alternately, we consider a synchrotron origin scenario for the GeV γ-ray outburst, which would work in a magnetically dominated jet. In this contribution, we present observational results of the outbursts in detail and discuss current problems on relativistic jets inferred from γ-ray observations.

Place, publisher, year, edition, pages
American Institute of Physics Inc. , 2017.
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:kth:diva-207379DOI: 10.1063/1.4968961ISI: 000399207800076ScopusID: 2-s2.0-85010960761ISBN: 9780735414563 OAI: oai:DiVA.org:kth-207379DiVA: diva2:1107551
Conference
6th International Symposium on High Energy Gamma-Ray Astronomy, 11 July 2016 through 15 July 2016
Note

 Funding details: ASI, Agenzia Spaziale Italiana; Funding details: CNRS, Centre National de la Recherche Scientifique; Funding details: DOE, U.S. Department of Energy; Funding details: INAF, Istituto Nazionale di Astrofisica; Funding details: INFN, Instituto Nazionale di Fisica Nucleare; Funding details: JAXA, Japan Aerospace Exploration Agency; Funding details: KEK, High Energy Accelerator Research Organization; Funding details: MEXT, Ministry of Education, Culture, Sports, Science and Technology; Funding details: NASA, National Aeronautics and Space Administration; Funding text: The Fermi-LAT Collaboration acknowledges support for LAT development, operation and data analysis from NASA and DOE (United States), CEA/Irfu and IN2P3/CNRS (France), ASI and INFN (Italy), MEXT, KEK, and JAXA (Japan), and the K.A.Wallenberg Foundation, the Swedish Research Council and the National Space Board (Sweden). Science analysis support in the operations phase from INAF (Italy) and CNES (France) is also gratefully acknowl- edged. M.H. acknowledges support by JSPS KAKENHI grant number JP15K17640.

QC 20170609

Available from: 2017-06-09 Created: 2017-06-09 Last updated: 2017-06-09Bibliographically approved

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CiteExportLink to record
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