Long-term gamma-ray and multiwavelength observations of 3C 454.3 (a.k.a. the Crazy Diamond)

TL;DR

This paper reports on an extensive multiwavelength observational campaign of the gamma-ray quasar 3C 454.3, revealing unprecedented high activity levels and variability, and includes spectral energy distribution modeling across different activity states.

Contribution

It provides the longest multiwavelength coverage of 3C 454.3, capturing unprecedented gamma-ray activity and variability, and analyzes inter-band lags and spectral energy distributions.

Findings

Record gamma-ray flux levels above 100 MeV.

Significant optical variability on hourly timescales.

Correlated multiwavelength activity and spectral modeling.

Abstract

During the period July 2007 - January 2009, the AGILE satellite, together with several other space- and ground-based observatories monitored the activity of the flat-spectrum radio quasar 3C 454.3, yielding the longest multiwavelength coverage of this gamma-ray quasar so far. The source underwent an unprecedented period of very high activity above 100 MeV, a few times reaching gamma-ray flux levels on a day time scale higher than F=400 x 10^-8 ph cm^-2 s^-1, in conjunction with an extremely variable behavior in the optical R-band, even of the order of several tenth of magnitude in few hours, as shown by the GASP-WEBT light curves. We present the results of this long term multiwavelength monitoring campaign, with particular emphasis on the study of possible lags between the different wavebands, and the results of the modeling of simultaneous spectral energy distributions at different levels of activity.