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Astronomy and Astrophysics Supplement Series, Vol. 119, October II 1996, 199-203
Infrared properties of OJ 287
You-Hong Zhang and Guang-Zhong Xie
Send offprint requests to: You-Hong Zhang
Yunnan Observatory, The Chinese Academy of Sciences, P.O. Box 110,
Kunming 650011, P.R. China
e-mail: ynaogh@public.bta.net.cn
Received December 7, 1995; accepted February 22, 1996
Abstract:
The paper presents the first evidence for the long-term near-infrared brightness, colour and spectral variability in the BL Lac object OJ 287. It had an infrared outburst of large amplitude during the beginning of 1983. The J-K colour index increased linearly, and infrared spectrum also linearly steepened during the years 1975-1990. After then, both the J-K colour and spectral index began to recover. Both the J-K colour and the near-infrared spectral index shows also a strong correlation with the flux intensity, in the sense that when OJ 287 is fainter, J-K is larger, and the near-infrared spectrum steeper. These properties show a very important similarity with the optical data of OJ 287 from the same time interval (Takalo & Sillanpää 1989). Our results argue that a single variable synchrotron source might be responsible for the photometric behaviour of OJ 287 in the near-infrared and optical regions.Key words: BL Lac objects: individual: OJ 287 --- infrared: galaxies
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