부산대학교 도서관

Seventeen southern sky BL Lacs were observed in UBVRI using the CCD Camera on the 1.0m telescope at the South African Astronomical Observatory (SAAO) in Aug and Nov 1999. The analyses of all the seventeen sources are now complete, and are available via anonymous ftp (ftp pukrs1.puk.ac.za/pub/Blazars). A few examples of our results are however given in this paper. Whereas PKS 2005-489 and PKS 2155-304 apear to have been in a high state, PKS 0048-097 and PKS 0521-365 showed evidence of variability on a time-scale of a few days, with the amplitude of variability increasing towards short wavelengths. This is consistent with observations of gamma-ray BL Lacs, which show similar behaviour in optical and X-rays.
Comment: 4 pages, 3 figures, Proceedings of the `Heidelberg International Symposium on High Energy Gamma-Ray Astronomy'