Rapid variability of blazar 3C 279 during flaring states in 2013-2014 with joint FERMI-LAT, NuSTAR, swift, and ground-based multi-wavelength observations

M. Hayashida, K. Nalewajko, G. M. Madejski, M. Sikora, R. Itoh, M. Ajello, R. D. Blandford, S. Buson, J. Chiang, Y. Fukazawa, A. K. Furniss, Finn Erland Christensen, Allan Hornstrup, Niels Jørgen Stenfeldt Westergaard

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Abstract

We report the results of a multiband observing campaign on the famous blazar 3C 279 conducted during a phase of increased activity from 2013 December to 2014 April, including first observations of it with NuSTAR. The γ-ray emission of the source measured by Fermi-LAT showed multiple distinct flares reaching the highest flux level measured in this object since the beginning of the Fermi mission, with F (E> 100 MeV) of 10-5 photons cm-2 s-1, and with a flux-doubling time scale as short as 2 hr. The y-ray spectrum during one of the flares was very hard, with an index of Γγ = 1.7 ± 0.1, which is rarely seen in flat-spectrum radio quasars. The lack of concurrent optical variability implies a very high Compton dominance parameter Lγ/Lsyn > 300. Two 1 day NuSTAR observations with accompanying Swift pointings were separated by 2 weeks, probing different levels of source activity. While the 0.5-70 keV X-ray spectrum obtained during the first pointing, and fitted jointly with Swift-XRT is well-described by a simple power law, the second joint observation showed an unusual spectral structure: the spectrum softens by ΔΓX ≃ 0.4 at ~4 keV. Modeling the broadband spectral energy distribution during this flare with the standard synchrotron plus inverse-Compton model requires: (1) the location of the'y-ray emitting region is comparable with the broad-line region radius, (2) a very hard electron energy distribution index p ≃ 1, (3) total jet power significantly exceeding the accretion-disk luminosity Lj/Ld ≳ 10, and (4) extremely low jet magnetization with LB/Lj 10-4. ≲ - We also find that single-zone models that match the observed γ-ray and optical spectra cannot satisfactorily explain the production of X-ray emission.
Original languageEnglish
Article number79
JournalAstrophysical Journal
Volume807
Number of pages18
ISSN0004-637X
DOIs
Publication statusPublished - 2015

Keywords

  • Galaxies: active
  • Galaxies: jets
  • Gamma rays: galaxies
  • Quasars: individual (3C 279)
  • Radiation mechanisms: non-thermal
  • X-rays: galaxies

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