Radio variability properties for radio sources^*

¹ Center for Astrophysics, Guangzhou University, Guangzhou 510006, PR China e-mail: fjh@gzhu.edu.cn
² Physics Institute, Hunan Normal University, Changsha, PR China
³ College of Science and Trade, Guangzhou University, Guangzhou 511442, PR China
⁴ Department of Physics and Electronics Science, Hunan University of Arts and Science, Changde 415000, PR China
⁵ Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai – 400005, India

Received: 25 December 2005
Accepted: 1 October 2006

Abstract

In this paper, we used the database of the university of Michigan Radio Astronomy Observatory (UMRAO) at three (4.8 GHz, 8.0 GHZ, and 14.5 GHz) radio frequency to analyze the radio light curves by the power spectral analysis method in search of possible periodicity. The analysis results showed that the radio sources display astrophysically meaningful periodicity ranging from 2.2 to 20.8 years in their light curves at the three frequencies. We also calculated the variability parameters and investigated the correlations between the variability parameter and the flux density. For the variability parameters, we found that the parameters at higher frequency are higher than those in the lower frequency. In addition, the variability parameters of BL Lacertae objects are larger than those of flat-spectrum radio quasars. suggesting that they are more variable than flat spectrum radio quasars.