AGILE detection of a strong gamma ray flare from the blazar S5 0716 714 during September-October 2007
Abstract
We report the γ -ray activity from the Intermediate BL Lac S5 0716+714 during 2007 September October observations by the AGILE satellite, coincident with a period of intense optical activity of the source monitored by GASP WEBT. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector (GRID) and the hard X-ray imager (Super-AGILE) sensitive in the energy range 30 MeV 50 GeV and 18 60 keV respectively, in two different periods: the first between 4 and 23 September 2007, the second between 24 October and 1 November 2007. Over the period 7 12 September, AGILE detected γ -ray emission from the source at a significance level of 9.6-σ with an average flux (E>100 MeV) of (97 ± 15) × 10-8 photons cm-2 s-1 , increas- ing by a factor of at least four within three days. No emission was detected by Super-AGILE in the energy range 18 60 keV, with a 3-σ upper limit of 10 mCrab in 335 ksec. The γ -ray flux of S5 0716+714 detected by AGILE is the highest ever detected for this blazar and one of the most intense γ -ray fluxes detected from a BL Lac object. The Spectral Energy Distribution (SED) of mid-September seems to be consistent with the synchrotron self-Compton (SSC) emission model, but only by including two SSC components with different variability. In October 2007 AGILE repointed toward S5 0716+714 following an intense optical flare, mea- suring an average flux of (47 ± 11) × 10-8 photons cm-2 s-1 at a significance level of 6.0-σ . The γ -ray flux during both AGILE pointings appears to be highly variable on timescales of 1 day.
- Publication:
-
Blazar Variability across the Electromagnetic Spectrum
- Pub Date:
- 2008
- DOI:
- 10.22323/1.063.0033
- arXiv:
- arXiv:0808.3673
- Bibcode:
- 2008bves.confE..33D
- Keywords:
-
- Astrophysics
- E-Print:
- 8 pages, 4 figures, "Workshop on Blazar Variability across the Electromagnetic Spectrum", 2008 April 22-25, Palaiseau, France