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Optical observations of BL Lacertae from 1997 to 1999

J. H. Fan·B. C. Qian·J. Tao
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Abstract

We present the optical (V, R, and I) photometry for BL Lacertae, which was observed from 1997 through 1999, with the 1.56-m telescope at the Shanghai astronomical observatory (SHAO). After the 1997 outburst, it dimmed to a low state and then brightened again. During the period JD 2450701 to JD 2450701.5, variations of 0.40mag, 0.27mag, and 0.21mag over a time scale of 100 minutes were found for V, R, and I bands, suggesting that the variations were decreasing with wavelength. The correlation between V, R, and I is also analyzed using the DCF (Discrete Correlation Function) method. This shows that the variability in the V, R, and I bands are correlated with no time delay longer than 0.2 day.

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J. H. Fan, B. C. Qian, J. Tao. 2001-03-03. Optical observations of BL Lacertae from 1997 to 1999. https://doi.org/10.1051/0004-6361%3A20010169

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