Historic Light Curve and Long-term Optical Variation of BL Lacertae 2200+420
Fan, J HCentre de Recherche Astronomique de Lyon, Observatoire de Lyon, 9 Avenue Charles André, 69 563 Saint-Genis-Laval Cedex, FranceXie, G ZYunnan Observatory, Chinese Academy of Sciences, Kunming 650011, ChinaPécontal, ECentre de Recherche Astronomique de Lyon, Observatoire de Lyon, 9 Avenue Charles André, 69 563 Saint-Genis-Laval Cedex, FrancePecontal, ACentre de Recherche Astronomique de Lyon, Observatoire de Lyon, 9 Avenue Charles André, 69 563 Saint-Genis-Laval Cedex, FranceCopin, YCentre de Recherche Astronomique de Lyon, Observatoire de Lyon, 9 Avenue Charles André, 69 563 Saint-Genis-Laval Cedex, France
1998en
ABI
Abstract
In this paper, historical optical(UBVRI) data and newly observed data from the Yunnan Observatory of China(about100 years) are presented for BL Lacertae. Maximum variations in UBVRI: 5.12, 5.31, 4.73, 2.59, and 2.54 and color indices of U-B = -0.11 +/- 0.20, B-V= 1.0 +/- 0.11, V-R= 0.73 +/- 0.19, V-I= 1.42 +/- 0.25, R-I= 0.82 +/- 0.11, and B-I= 2.44 +/- 0.29 have been obtained from the literature; The Jurkevich method is used to investigate the existence of periods in the B band light curve, and a long-term period of 14 years is found. The 0.6 and 0.88 year periods reported by Webb et al.(1988) are confirmed. In addition, a close relation between B-I and B is found, suggesting that the spectra flattens when the source brightens.
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