AGILE observation of a gamma-ray flare from the blazar 3C 279

TL;DR

The AGILE satellite detected a significant gamma-ray flare from the blazar 3C 279 in July 2007, providing valuable multiwavelength data to analyze its spectral energy distribution and test theoretical emission models.

Contribution

This study presents the first simultaneous gamma-ray, X-ray, and optical observations of a flare from 3C 279, offering new insights into its emission mechanisms during high activity.

Findings

Detected gamma-ray flux of (210+-38) x 10^-8 ph cm^-2 s^-1 above 100 MeV.

No significant gamma-ray flux variation during the 4-day observation.

SED modeled with a one-zone Synchrotron Self Compton and external Compton scattering components.

Abstract

Context. We report the detection by the AGILE satellite of an intense gamma-ray flare from the gamma-ray source 3EG J1255-0549, associated to the Flat Spectrum Radio Quasar 3C 279, during the AGILE pointings towards the Virgo Region on 2007 July 9-13. Aims. The simultaneous optical, X-ray and gamma-ray covering allows us to study the spectral energy distribution (SED) and the theoretical models relative to the flaring episode of mid-July. Methods. AGILE observed the source during its Science Performance Verification Phase with its two co-aligned imagers: the Gamma- Ray Imaging Detector (GRID) and the hard X-ray imager (Super-AGILE) sensitive in the 30 MeV - 50 GeV and 18 - 60 keV respectively. During the AGILE observation the source was monitored simultaneously in optical band by the REM telescope and in the X-ray band by the Swift satellite through 4 ToO observations. Results. During 2007 July 9-13 July 2007, AGILE-GRID detected gamma-ray emission from 3C 279, with the source at ~2 deg from the center of the Field of View, with an average flux of (210+-38) 10^-8 ph cm^-2 s^-1 for energy above 100 MeV. No emission was detected by Super-AGILE, with a 3-sigma upper limit of 10 mCrab. During the observation lasted about 4 days no significative gamma-ray flux variation was observed. Conclusions. The Spectral Energy Distribution is modelled with a homogeneous one-zone Synchrotron Self Compton emission plus the contributions by external Compton scattering of direct disk radiation and, to a lesser extent, by external Compton scattering of photons from the Broad Line Region.