Charge coupled devices (CCD) photometry and long-term optical variability of gamma-ray-loud BL Lacertae object Mkn 421
Zhang Xiong(张雄)a)c)†, Zheng Yong-Gang(郑永刚)a), Zhang Hao-Jing(张皓晶)b), Hu Shao-Ming(胡绍明)b), and Xie Zhao-Hua(谢照华)a)
a Department of Physics, Yunnan Normal University, Kunming 650092, China; b National Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, China; c Department of Physics, The University of Hong Kong, China
Abstract Evidence for the long-term optical curve variability and colour behaviour of the BL Lac object Mkn 421 is presented. Our results show that the amplitude of the optical variations of Mkn 421 is only about $\Delta B=4.7$ magnitude in the B-band for its photometric history from 1899 to 2002. The results of optical photometric monitoring of the Mkn 421 from April 2000 to Jan 2002 are provided. During our observation, Mkn 421 shows significant rapid variations and exhibits short time variability of 2.42 hours in the B band. A strong correlation between the B-V colour index and the magnitude in the B band is found. Our charge coupled device (CCD) photometry of Mkn 421 shows that the measured results are in good agreement with the predicted optical variability period of about 23 years.
Received: 12 January 2006
Revised: 15 May 2006
Accepted manuscript online:
Fund: Project supported by an CRCG grant of
the University of Hong Kong, Yunnan Provincial Foundation of Science of China
\linebreak \makebox[1.6mm]{}(Grant No 2004A0027M) and the National Natural Science
Foundation of China(Grant No 10363002), and the Natural Science\linebreak
\makebox[1.6mm]{}Foundation of China Education Department(Grant No 02142).
Cite this article:
Zhang Xiong(张雄), Zheng Yong-Gang(郑永刚), Zhang Hao-Jing(张皓晶), Hu Shao-Ming(胡绍明), and Xie Zhao-Hua(谢照华) Charge coupled devices (CCD) photometry and long-term optical variability of gamma-ray-loud BL Lacertae object Mkn 421 2006 Chinese Physics 15 2185
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