Correlated variability in the blazar 3C 454.3

TL;DR

This study presents a multi-wavelength analysis of blazar 3C 454.3 during a high flux state, revealing correlated variability across IR, optical, UV, and gamma-ray bands, supporting an external Compton emission model.

Contribution

It provides detailed observational evidence of correlated multi-wavelength variability in 3C 454.3, supporting the external Compton model for blazar emission.

Findings

Strong correlation between IR, optical, UV, and gamma-ray light curves.

Infrared variability amplitude is comparable to gamma-rays and larger than optical/UV.

X-ray flux shows weak correlation with other wavelengths.

Abstract

The blazar 3C 454.3 was revealed by the Fermi Gamma-ray Space Telescope to be in an exceptionally high flux state in July 2008. Accordingly, we performed a multi-wavelength monitoring campaign on this blazar using IR and optical observations from the SMARTS telescopes, optical, UV and X-ray data from the Swift satellite, and public-release gamma-ray data from Fermi. We find an excellent correlation between the IR, optical, UV and gamma-ray light curves, with a time lag of less than one day. The amplitude of the infrared variability is comparable to that in gamma-rays, and larger than at optical or UV wavelengths. The X-ray flux is not strongly correlated with either the gamma-rays or longer wavelength data. These variability characteristics find a natural explanation in the external Compton model, in which electrons with Lorentz factor gamma~10^(3-4) radiate synchrotron emission in the infrared-optical and also scatter accretion disk or emission line photons to gamma-ray energies, while much cooler electrons (gamma~10^(1-2)) produce X-rays by scattering synchrotron or other ambient photons.