Rapid Variability of Blazar 3C 279 during Flaring States in 2013-2014 with Joint Fermi-LAT, NuSTAR, Swift, and Ground-Based Multi-wavelength Observations
Creators: name: Hayashida, M.
name: Nalewajko, K.
name: Madejski, G. M.
name: Sikora, M.
name: Itoh, R.
name: Ajello, M.
name: Blandford, R. D.
name: Buson, S.
name: Chiang, J.
name: Fukazawa, Y.
name: Furniss, A. K.
name: Urry, C. M.
name: Hasan, I.
name: Harrison, F. A.
name: Alexander, D. M.
name: Baloković, M.
name: Barret, D.
name: Boggs, S. E.
name: Christensen, F. E.
name: Craig, W. W.
name: Forster, K.
name: Giommi, P.
name: Grefenstette, B.
name: Hailey, C.
name: Hornstrup, A.
name: Kitaguchi, T.
name: Koglin, J. E.
name: Madsen, K. K.
name: Mao, P. H.
name: Miyasaka, H.
name: Mori, K.
name: Perri, M.
name: Pivovaroff, M. J.
name: Puccetti, S.
name: Rana, V.
name: Stern, D.
name: Tagliaferri, G.
name: Westergaard, N. J.
name: Zhang, W. W.
name: Zoglauer, A.
name: Gurwell, M. A.
name: Uemura, M.
name: Akitaya, H.
name: Kawabata, K. S.
name: Kawaguch, K.
name: Kanda, Y.
name: Moritani, Y.
name: Takaki, K.
name: Ui, T.
name: Yoshida, M.
name: Agarwal, A.
name: Gupta, A. C.
Publisher: name: arXiv
Year: 2015
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the results of a multi-band 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 $F(E &gt; 100\,{\rm MeV})$ of $10^{-5}$ photons cm$^{-2}$ s$^{-1}$, and with a flux doubling time scale as short as 2 hours. The $γ$-ray spectrum during one of the flares was very hard, with an index of $Γ_γ= 1.7 \pm 0.1$, which is rarely seen in flat spectrum radio quasars. The lack of concurrent optical variability implies a very high Compton dominance parameter $L_γ/L_{\rm syn} &gt; 300$. 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 $ΔΓ_{\rm X} \simeq 0.4$ at $\sim$4 keV. Modeling the broad-band SED 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 $p \simeq 1$, (3) total jet power significantly exceeding the accretion disk luminosity $L_{\rm j}/L_{\rm d} \gtrsim 10$, and (4) extremely low jet magnetization with $L_{\rm B}/L_{\rm j} \lesssim 10^{-4}$. 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.
description: 17 pages, 10 figures, accepted for publication in The Astrophysical Journal