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Rapid variability of blazar 3C 279 during flaring states in 2013-2014 with joint Fermi-LAT, NuSTAR, Swift, and ground-based multiwavelength observations.

Hayashida, M. and Nalewajko, K. and Madejski, G.M. and Sikora, M. and Itoh, R. and Ajello, M. and Blandford, R.D. and Buson, S. and Chiang, J. and Fukazawa, Y. and Furniss, A.K. and Urry, C.M. and Hasan, I. and Harrison, F.A. and Alexander, D.M. and Baloković, M. and Barret, D. and Boggs, S.E. and Christensen, F.E. and Craig, W.W. and Forster, K. and Giommi, P. and Grefenstette, B. and Hailey, C. and Hornstrup, A. and Kitaguchi, T. and Koglin, J.E. and Madsen, K.K. and Mao, P.H. and Miyasaka, H. and Mori, K. and Perri, M. and Pivovaroff, M.J. and Puccetti, S. and Rana, V. and Stern, D. and Tagliaferri, G. and Westergaard, N.J. and Zhang, W.W. and Zoglauer, A. and Gurwell, M.A. and Uemura, M. and Akitaya, H. and Kawabata, K.S. and Kawaguchi, K. and Kanda, Y. and Moritani, Y. and Takaki, K. and Ui, T. and Yoshida, M. and Agarwal, A. and Gupta, A.C. (2015) 'Rapid variability of blazar 3C 279 during flaring states in 2013-2014 with joint Fermi-LAT, NuSTAR, Swift, and ground-based multiwavelength observations.', Astrophysical journal., 807 (1). p. 79.


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 γ-ray spectrum during one of the flares was very hard, with an index of Γ= ± γ 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 ΔΓ ≃ X 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 γ-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 L j d L ≳ 10, and (4) extremely low jet magnetization with ≲ − LB j L 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.

Item Type:Article
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Publisher statement:© 2015. The American Astronomical Society. All rights reserved.
Date accepted:31 March 2015
Date deposited:22 June 2016
Date of first online publication:02 July 2015
Date first made open access:No date available

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