Optical observations of BL Lacertae from 1997 to 1999
J. H. FanChinese Academy of Science-Peking University Joint Beijing Astrophysical Center (CAS-PKU.BAC), Beijing, PR ChinaB. C. QianShanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, PR ChinaJun TaoShanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, PR China
2001en
ABI
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 ion state and then brightened again. During the period JD 2450701 to JD 2450701.5, variations of 0.80 mag, 0.27 mag, and 0.21 mag over a time scale of 100 min 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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Cited by 20 references