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A Spectacular VHE Gamma-Ray Outburst from PKS 2155-304 in 2006

Abstract : 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.
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Contributor : Dominique Girod <>
Submitted on : Monday, October 1, 2007 - 12:59:46 PM
Last modification on : Monday, June 7, 2021 - 3:38:38 AM


  • HAL Id : in2p3-00175788, version 1


W. Benbow, C. Boisson, L. Costamante, O. de Jager, G. Dubus, et al.. A Spectacular VHE Gamma-Ray Outburst from PKS 2155-304 in 2006. 30th International Cosmic Ray Conference - ICRC 07, Jul 2007, Merida, Mexico. pp.1081-1084. ⟨in2p3-00175788⟩



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