The implications from CANGAROO-III observations of TeV blazar PKS   2155-304
  We have observed the high-frequency-peaked BL Lacertae object PKS2155-304 in 2004, 2005 and 2006 with the CANGAROO-III imaging atmospheric Cherenkov telescope, and have detected a signal above 660 GeV at the 4.8/sigma level during the 2006 outburst period. Intranight flux variability on time scale of half an hour is observed. From this variability time scale, the size of the TeV gamma-ray emission region is restricted to 5x10^13\delta cm, and the super massive black hole mass is estimated to be less than 1.9x10^8\delta M_{Solar}, where \delta is the beaming factor. The differential energy spectrum is obtained, and an upper limit of the extragalactic infrared background light (EBL) flux is derived under some assumption. We also fit a synchrotron self Compton (SSC) model to the spectral energy distribution (SED) and derive the beaming factor and magnetic field strength. 
K. Nishijima, Y. Sakamoto, J. Kushida, K. Saito (the CANGAROO-III   Collaboration)