Abstract. Seven BL Lac objects have been photometri-cally observed in an eort to study the dierence of optical intraday variability between the radio-selected BL Lac ob-jects (RBLs) and X-ray-selected BL Lac objects (XBLs). The objects we observed are selected arbitrarily. They are four RBLs, PKS 0735+178, PKS 0754+101, OJ 287 and BL Lac, and three XBLs, H 0323+022, H 0548−322 and H 2154−304. During the observation all of them exhibited microvariation, and H 0323+022 and H 0548−322 some-times showed brightness oscillation. PKS 0735+178 and BL Lac were in their faint states and not very active. It seems that RBLs do not show microvariability more fre-quently than XBLs. Key words: BL Lacertae objects: general | galaxies: photometry 1
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