AGILE detection of variable gamma-ray activity from the blazar S5 0716+714 in September-October 2007
Creators: name: Chen, A. W.
name: D'Ammando, F.
name: Villata, M.
name: Raiteri, C. M.
name: Tavani, M.
name: Vittorini, V.
name: Bulgarelli, A.
name: Donnarumma, I.
name: Ferrari, A.
name: Giuliani, A.
name: Longo, F.
name: Pacciani, L.
name: Pucella, G.
name: Vercellone, S.
name: Argan, A.
name: Barbiellini, G.
name: Boffelli, F.
name: Caraveo, P.
name: Carosati, D.
name: Cattaneo, P. W.
name: Cocco, V.
name: Costa, E.
name: Del Monte, E.
name: De Paris, G.
name: Di Cocco, G.
name: Evangelista, Y.
name: Feroci, M.
name: Fiorini, M.
name: Froysland, T.
name: Frutti, M.
name: Fuschino, F.
name: Galli, M.
name: Gianotti, F.
name: Kurtanidze, O. M.
name: Labanti, C.
name: Lapshov, I.
name: Larionov, V. M.
name: Lazzarotto, F.
name: Lipari, P.
name: Marisaldi, M.
name: Mastropietro, M.
name: Mereghetti, S.
name: Morelli, E.
name: Morselli, A.
name: Pasanen, M.
name: Pellizzoni, A.
name: Perotti, F.
name: Picozza, P.
name: Porrovecchio, G.
name: Prest, M.
name: Rapisarda, M.
name: Rappoldi, A.
name: Rubini, A.
name: Soffitta, P.
name: Trifoglio, M.
name: Trois, A.
name: Vallazza, E.
name: Zambra, A.
name: Zanello, D.
name: Cutini, S.
name: Gasparrini, D.
name: Pittori, C.
name: Santolamazza, P.
name: Verrecchia, F.
name: Giommi, P.
name: Antonelli, L. A.
name: Colafrancesco, S.
name: Salotti, L.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the gamma-ray activity from the intermediate BL Lac S5 0716+714 during observations acquired by the AGILE satellite in September and October 2007. These detections of activity were contemporaneous with a period of intense optical activity, which was monitored by GASP-WEBT. This simultaneous optical and gamma-ray coverage allows us to study in detail the light curves, time lags, gamma-ray photon spectrum, and Spectral Energy Distributions (SEDs) during different states of activity. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector (GRID) and the hard X-ray imager (Super-AGILE), which are sensitive to the 30 MeV-50 GeV and 18-60 keV energy ranges, respectively. Observations were completed in two different periods, the first between 2007 September 4-23, and the second between 2007 October 24-November 1. Over the period 2007 September 7-12, AGILE detected gamma-ray emission from the source at a significance level of 9.6-sigma with an average flux (E&gt;100 MeV) of (97 +/- 15) x 10^{-8} photons cm^{-2} s^{-1}, which increased by a factor of at least four within three days. No emission was detected by Super-AGILE for the energy range 18-60 keV to a 3-sigma upper limit of 10 mCrab in 335 ksec. In October 2007, AGILE repointed toward S5 0716+714 following an intense optical flare, measuring an average flux of (47 +/- 11) x 10^{-8} photons cm^{-2} s^{-1} at a significance level of 6.0-sigma. The gamma-ray flux of S5 0716+714 detected by AGILE is the highest ever detected for this blazar and one of the most intense gamma-ray fluxes detected from a BL Lac object. The SED of mid-September appears to be consistent with the synchrotron self-Compton (SSC) emission model, but only by including two SSC components of different variabilities.
description: 5 pages, 5 figures, accepted by A&amp;A Letters 18/8/2008