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30th International Cosmic Ray Conference - ICRC 07, Merida : Mexique (2007)
A Spectacular VHE Gamma-Ray Outburst from PKS 2155-304 in 2006
W. Benbow, C. Boisson1, L. Costamante, O. De Jager, G. Dubus2, D. Emmanoulopoulos, B. Giebels3, S. Pita4, M. Punch4, C. Raubenheimer, M. Raue, H. Sol1, S. Wagner
HESS Collaboration(s)

Since 2002 the VHE (>100 GeV) gamma-ray flux of the high-frequency peaked BL Lac PKS 2155-304 has been monitored with the High Energy Stereoscopic System (HESS). An extreme gamma-ray outburst was detected in the early hours of July 28, 2006 (MJD 53944). The average flux above 200 GeV observed during this outburst is ~7 times the flux observed from the Crab Nebula above the same threshold. Peak fluxes are measured with one-minute time scale resolution at more than twice this average value. Variability is seen up to ~600 s in the Fourier power spectrum, and well-resolved bursts varying on time scales of ~200 seconds are observed. There are no strong indications for spectral variability within the data. Assuming the emission region has a size comparable to the Schwarzschild radius of a ~10^9 solar mass black hole, Doppler factors greater than 100 are required to accommodate the observed variability time scales.
1 :  LUTH - Laboratoire Univers et Théories
2 :  LAOG - Laboratoire d'Astrophysique de Grenoble
3 :  LLR - Laboratoire Leprince-Ringuet
4 :  APC - UMR 7164 - AstroParticule et Cosmologie
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique