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Astron. Astrophys. Suppl. Ser. 133, 217-220

Infrared variability of BL Lacertae

J.H. Fan1,2 - G.Z. Xie3 - R.G. Lin 2 - Y.P. Qin3

1 - CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, China
2 - Center for Astrophysics, Guangzhou Normal University, Guangzhou 510400, China
3 - Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China

Received November 24, 1997; accepted June 10, 1998


In this paper, the historic light curves of BL Lacertae in the infrared (JHK) bands have been constructed from the published literature. Maximum variations of $\Delta J = 2\hbox{$.\!\!^{\rm m}$}29$, $\Delta H = 2\hbox{$.\!\!^{\rm m}$}42$, and $\Delta K
= 2\hbox{$.\!\!^{\rm m}$}93$ and average color indices of $J-H = 0.78 \pm 0.11$, $H-K = 0.78
\pm 0.12$, and $J-K = 1.55 \pm 0.13$ have been found. The relation between the color index and the brightness of the source and the correlation of color-color indices have been investigated. Our analysis shows that there is no clear correlation between the color index and the brightness, and the emission mechanism is non-thermal in the near-infrared.

Key words: infrared: galaxies -- BL Lacertae objects: BL Lac

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