Multiwavelength Variations of 3C 454.3 during the November 2010 to January 2011 Outburst

TL;DR

This study presents comprehensive multiwavelength observations of the blazar 3C 454.3 during a bright outburst, revealing simultaneous high-energy variations and proposing a jet shock model to explain the emission mechanisms.

Contribution

It provides the first extensive, nearly two-month, multiwavelength dataset of 3C 454.3 during an outburst, with detailed spectral energy distributions and a physical model of jet emission.

Findings

Simultaneous variability observed across millimeter, far-infrared, and gamma-ray bands.

The outburst site is located in the parsec-scale core, with a 70% flux increase.

The proposed model explains high-energy emission via inverse Compton scattering at a standing shock.

Abstract

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.