TeV gamma-ray observations of Southern BL Lacs with the CANGAROO 3.8m Imaging Telescope

Observational and theoretical results indicate that low-redshift BL Lacertae objects are the most likely extragalactic sources to be detectable at TeV energies. In this paper we present the results of observations of 4 BL Lacertae objects (PKS0521 365, EXO0423.4 0840, PKS2005 489 and PKS2316 423) made between 1993 and 1996 with the CANGAROO 3.8m imaging Cerenkov telescope. During the period of these observations the gamma-ray energy threshold of the 3.8m telescope was 2TeV. Searches for steady long-term emission have been made, and, inspired by the TeV ares detected from Mkn 421 and Mkn 501, a search on a night-by-night timescale has also been performed for each source. Comprehensive Monte Carlo simulations are used to estimate upper limits for both steady and short timescale emission.