TeV gamma-ray observations of three X-ray selected BL Lacs

Despite extensive surveys of extragalactic TeV gamma-ray candidates only 3 sources have so far been de- tected. All three are northern hemisphere objects and all three are low-redshift X-ray selected BL Lacs (XBLs). In this pa- per we present the results of observations of the three near- est southern hemisphere XBLs (PKS0548-322, PKS2005-489 and PKS2155-304) with the CANGAROO 3.8m imaging tele- scope. During the period of observation we estimate that the threshold of the 3.8 m telescope was 1.5 TeV. Searches for both steady and short timescale emission have been performed for each source. Additionally, we are able to monitor the X-ray state of each source on a daily basis and we have made contem- poraneous measurements of optical activity for PKS0548-322 and PKS2155-304.