Multiwavelength Variations of 3C 454.3 during the November 2010 to
  January 2011 Outburst
  We present multiwavelength data of the blazar 3C 454.3 obtained during an
extremely bright outburst from November 2010 through January 2011. These
include flux density measurements with the Herschel Space Observatory at five
submillimeter-wave and far-infrared bands, the Fermi Large Area Telescope at
gamma-ray energies, Swift at X-ray, ultraviolet (UV), and optical frequencies,
and the Submillimeter Array at 1.3 mm. From this dataset, we form a series of
52 spectral energy distributions (SEDs) spanning nearly two months that are
unprecedented in time coverage and breadth of frequency. Discrete correlation
anlaysis of the millimeter, far-infrared, and gamma-ray light curves show that
the variations were essentially simultaneous, indicative of co-spatiality of
the emission, at these wavebands. In contrast, differences in short-term
fluctuations at various wavelengths imply the presence of inhomegeneities in
physical conditions across the source. We locate the site of the outburst in
the parsec-scale core, whose flux density as measured on 7 mm Very Long
Baseline Array images increased by 70 percent during the first five weeks of
the outburst. Based on these considerations and guided by the SEDs, we propose
a model in which turbulent plasma crosses a conical standing shock in the
parsec-scale region of the jet. Here, the high-energy emission in the model is
produced by inverse Compton scattering of seed photons supplied by either
nonthermal radiation from a Mach disk, thermal emission from hot dust, or (for
X-rays) synchrotron radiation from plasma that crosses the standing shock. For
the two dates on which we fitted the model SED to the data, the model
corresponds very well to the observations at all bands except at X-ray
energies, where the spectrum is flatter than observed.
