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A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279


It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight1. The size of the emitting zone and the location of this region relative to the central supermassive black hole are, however, poorly known, with estimates ranging from light-hours to a light-year or more. Here we report the coincidence of a gamma (γ)-ray flare with a dramatic change of optical polarization angle. This provides evidence for co-spatiality of optical and γ-ray emission regions and indicates a highly ordered jet magnetic field. The results also require a non-axisymmetric structure of the emission zone, implying a curved trajectory for the emitting material within the jet, with the dissipation region located at a considerable distance from the black hole, at about 105 gravitational radii.

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Figure 1: History of flux in various bands, γ-ray photon index, and optical polarization of 3C 279.
Figure 2: Energy spectrum from radio to γ-ray band of 3C 279 at two different epochs.

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Acknowledgements The Fermi-LAT Collaboration acknowledges support from a number of agencies and institutes for both development and the operation of the LAT as well as scientific data analysis. These include NASA and DOE in the United States, CEA/Irfu and IN2P3/CNRS in France, ASI and INFN in Italy, MEXT, KEK and JAXA in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the National Space Board in Sweden. Additional support from INAF in Italy for science analysis during the operations phase is also gratefully acknowledged. The GASP-WEBT observatories participating in this work are Abastumani, Calar Alto, Campo Imperatore, Crimean, Kitt Peak (MDM), L'Ampolla, Lowell (Perkins-PRISM), Lulin, Roque de los Muchachos (KVA and Liverpool), San Pedro Mártir, St Petersburg for the optical–NIR bands, and Mauna Kea (SMA), Medicina, Metsahovi, Noto and UMRAO for the millimetre radio band, and are supported in part by the Georgian National Science Foundation, the Spanish “Ministerio de Ciencia e Innovación”, the NSF and NASA and the Smithsonian Institution in the United States, the UK Science and Technology Facilities Council, the Academia Sinica in Taiwan, the Russian RFBR and the Academy of Finland. M.H. is supported by the JSPS for the Postdoctoral Fellowship for Research Abroad. J. Conrad is a Royal Swedish Academy of Sciences Research Fellow, funded by a grant from the K. A. Wallenberg Foundation. L.T. is partially supported by the International Doctorate on Astroparticle Physics (IDAPP) programme.

Author Contributions All authors contributed to the work presented in this paper. M. Uemura and R. Itoh led the Kanata observations and data analysis. M. Villata organized the optical-radio observations by GASP-WEBT as the president of the collaboration.

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Correspondence to M. Hayashida or G. M. Madejski.

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The Fermi-LAT Collaboration and members of the 3C 279 multi-band campaign. A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279. Nature 463, 919–923 (2010).

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