Multi-wavelength Observations of the Flaring Gamma-ray Blazar 3C 66A in 2008 October

TL;DR

This paper presents multi-wavelength observations of the blazar 3C 66A during a flare in October 2008, revealing correlated variability across gamma-ray to optical bands and modeling its spectral energy distribution.

Contribution

It provides comprehensive multi-wavelength data and demonstrates that external radiation fields are necessary to explain intra-night optical variability.

Findings

Correlated flares observed in optical and gamma-ray bands.

Spectral energy distribution fits favor models with external radiation fields.

Intra-night optical variability explained by external radiation field models.

Abstract

The BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fit using standard leptonic models with and without an external radiation field for inverse-Compton scattering. It is found, however, that only the model with an external radiation field can accommodate the intra-night variability observed at optical wavelengths.