The optical variability of two X-ray-selected and nine radio-selected BL Lac objects

CCD photometry for two x-ray-selected and nine radio-selected BL Lac objects, and one QSO, have been obtained at Yunnan Observatory. The main results show that: (1) IE 0317 + 186 has a short characteristic timescale of about 4.5 hr with amplitudes of {DELTA}V = 0.8 mag and {DELTA}R = 0.52 mag in the visual and red, respectively. (2) ON +231 has shown a variability on a short timescale of about 103 min with an amplitude of {DELTA}B = 0.8 mag. (3) OJ 287 has not shown a previously reported variability on a short timescale of 15.7 min in the B band.

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