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Astron. Astrophys. 337, 25-30 (1998)

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

M.D. Roberts 1, 2, S.A. Dazeley 2, P.G. Edwards 3, T. Hara 4, Y. Hayami 5, J. Holder 1, F. Kakimoto 5, S. Kamei 5, A. Kawachi 1, T. Kifune 1, R. Kita 6, T. Konishi 7, A. Masaike 8, Y. Matsubara 9, T. Matsuoka 9, Y. Mizumoto 10, M. Mori 1, H. Muraishi 6, Y. Muraki 9, K. Nishijima 12, S. Oda 7, S. Ogio 5, J.R. Patterson 2, G.P. Rowell 1, 2, T. Sako 9, K. Sakurazawa 5, R. Susukita 13, A. Suzuki 7, R. Suzuki 5, T. Tamura 14, T. Tanimori 5, G.J. Thornton 2, S. Yanagita 6, T. Yoshida 6 and T. Yoshikoshi 1

1 Institute for Cosmic Ray Research, University of Tokyo, Tokyo 188, Japan
2 Department of Physics and Mathematical Physics, University of Adelaide, South Australia 5005, Australia
3 Institute of Space and Astronautical Science, Kanagawa 229, Japan
4 Faculty of Commercial Science, Yamanashi Gakuin University, Yamanashi 400, Japan
5 Department of Physics, Tokyo Institute of Technology, Tokyo 152, Japan
6 Faculty of Science, Ibaraki University, Ibaraki 310, Japan
7 Department of Physics, Kobe University, Hyogo 637, Japan
8 Department of Physics, Kyoto University, Kyoto 606, Japan
9 Solar-Terrestrial Environment Laboratory, Nagoya University, Aichi 464, Japan
10 National Astronomical Observatory of Japan, Tokyo 181, Japan
11 Faculty of Education, Miyagi University of Education, Miyagi 980, Japan
12 Department of Physics, Tokai University, Kanagawa 259, Japan
13 Institute of Physical and Chemical Research, Saitama 351-01, Japan
14 Faculty of Engineering, Kanagawa University, Kanagawa 221, Japan

Received 27 February 1998 / Accepted 9 June 1998


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, EXO 0423.4-0840, PKS2005-489 and PKS2316-423) made between 1993 and 1996 with the CANGAROO 3.8 m imaging erenkov telescope. During the period of these observations the gamma-ray energy threshold of the 3.8m telescope was [FORMULA]2 TeV. Searches for steady long-term emission have been made, and, inspired by the TeV flares 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.

Key words: gamma-rays: observations – BL Lacertae objects: individual: PKS0521-365, EXO 0423.4-0840, PKS2005-489, PKS2316-423

Send offprint requests to: M.D. Roberts

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© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998