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We perform a multi-wavelength polarimetric study of the quasar CTA 102 during an extraordinarily bright $gamma$-ray outburst detected by the {it Fermi} Large Area Telescope in September-October 2012 when the source reached a flux of F$_{>100~mathrm{MeV}} =5.2pm0.4times10^{-6}$ photons cm$^{-2}$ s$^{-1}$. At the same time the source displayed an unprecedented optical and NIR outburst. We study the evolution of the parsec scale jet with ultra-high angular resolution through a sequence of 80 total and polarized intensity Very Long Baseline Array images at 43 GHz, covering the observing period from June 2007 to June 2014. We find that the $gamma$-ray outburst is coincident with flares at all the other frequencies and is related to the passage of a new superluminal knot through the radio core. The powerful $gamma$-ray emission is associated with a change in direction of the jet, which became oriented more closely to our line of sight ($thetasim$1.2$^{circ}$) during the ejection of the knot and the $gamma$-ray outburst. During the flare, the optical polarized emission displays intra-day variability and a clear clockwise rotation of EVPAs, which we associate with the path followed by the knot as it moves along helical magnetic field lines, although a random walk of the EVPA caused by a turbulent magnetic field cannot be ruled out. We locate the $gamma$-ray outburst a short distance downstream of the radio core, parsecs from the black hole. This suggests that synchrotron self-Compton scattering of near-infrared to ultraviolet photons is the probable mechanism for the $gamma$-ray production.
The blazar Mrk 421 shows frequent, short flares in the TeV energy regime. Due to the fast nature of such episodes, we often fail to obtain sufficient simultaneous information about flux variations in several energy bands. To overcome this lack of mul
After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September-October. The flare was tracked from gamma-ray to near-infrared frequencies, including Fermi and Swift data as well as photometric and polarimetr
The blazar 3C454.3 exhibited a strong flare seen in gamma-rays, X-rays, and optical/NIR bands during 3--12 December 2009. Emission in the V and J bands rose more gradually than did the gamma-rays and soft X-rays, though all peaked at nearly the same
Long-lasting, very bright multiwavelength flares of blazar jets are a curious phenomenon. The interaction of a large gas cloud with the jet of a blazar may serve as a reservoir of particles entrained by the jet. The size and density structure of the
We present a multi-wavelength study of the FSRQ CTA 102 using Fermi-LAT and simultaneous Swift-XRT/UVOT observations. The Fermi-LAT telescope detected one of the brightest flares from this object during Sep, 2016 to Mar, 2017. In the 190 days of obse