Volume 494, Number 2, February I 2009
|Page(s)||509 - 513|
|Published online||27 November 2008|
AGILE observation of a gamma-ray flare from the blazar 3C 279
INAF/IASF–Milano, via E. Bassini 15, 20133 Milano, Italy e-mail: firstname.lastname@example.org
2 INAF/IASF–Roma, via Fosso del Cavaliere 100, 00133 Roma, Italy
3 Dip. di Fisica, Univ. “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy
4 CIFS–Torino, Viale Settimio Severo 3, 10133 Torino, Italy
5 INAF/IASF–Bologna, via Gobetti 101, 40129 Bologna, Italy
6 Dip. di Fisica and INFN, via Valerio 2, 34127 Trieste, Italy
7 Dip. di Fisica, Univ. di Perugia, via Pascoli, 06123 Perugia, Italy
8 INFN–Pavia, via Bassi 6, 27100 Pavia, Italy
9 Dip. Fisica Nucleare e Teorica, Univ. di Pavia, via Bassi 6, 27100 Pavia, Italy
10 ENEA–Bologna, via dei Martiri di Monte Sole 4, 40129 Bologna, Italy
11 INFN–Roma “La Sapienza”, Piazzale A. Moro 2, 00185 Roma, Italy
12 INFN–Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy
13 Dip. di Fisica, Univ. dell'Insubria, via Valleggio 11, 22100 Como, Italy
14 ENEA–Roma, via E. Fermi 45, 00044 Frascati (Roma), Italy
15 ASI–ASDC, via G. Galilei, 00044 Frascati (Roma), Italy
16 ASI, Viale Liegi 26, 00198 Roma, Italy
Accepted: 10 October 2008
Context. We report the detection by the AGILE satellite of an intense gamma-ray flare from the gamma-ray source 3EG J1255-0549, associated with 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 mid-July flaring episode.
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 the optical band by the REM telescope and in the X-ray band by the Swift satellite through 4 target of opportunity observations.
Results. During 2007 July 9-13, AGILE-GRID detected gamma-ray emission from 3C 279, with the source at ~2° 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-σ upper limit of 10 mCrab. During the observation, which 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 the direct disk radiation and, to a lesser extent, by external Compton scattering of photons from the Broad Line Region.
Key words: gamma rays: observations / galaxies: quasars: individual: 3C 279
© ESO, 2009
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