2007/09/28 by W. Benbow, C. Boisson, Benbow, W. +24
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.48550/arxiv.0709.4608
4 pages, 3 figures; To appear in the Proceedings of the 30th ICRC (Merida, Mexico)
arxiv created 2007/09/28 · openalex publication_date 2007/09/28 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 ~109 solar mass black hole, Doppler factors greater than 100 are required to accommodate the observed variability time scales.