The deviation of optical variability of radio-quiet quasars from damped random walk

  • Hongtao Wang
  • Yong ShiEmail author
Original Article


In this work, we examine the consistency of quasar optical flux variability with the damped random walk (DRW) model. Our sample includes 144 radio quiet quasars selected from DR7 SDSS quasar catalog randomly, with the redshift \(0.3 < z < 1.0 \), \(10^{8.0} M_{\odot} < M_{\mathrm {BH}} < 10^{9.9} M_{\odot}\) and the luminosity \(\lambda L(\lambda, {5100~\mathring{\mathrm{A}}} )\) larger than \(10^{45}~\mbox{erg}\,\mbox{s}^{-1}\). We measure the first-order structure function of their light curves and model the results with four parameters described by the power exponential (PE) covariance matrix, and we further utilize the Markov Chain Monte Carlo (MCMC) method to obtain four reliable parameter value. The main results are listed as follows: (1) The ensemble structure function of 144 sources is consistent with the DRW model. (2) From the individual analytical result, we find 10 objects deviated from the DRW model (\(\beta=1\)) at 5\(\sigma\) levels and the simulation result indicate the reliability of \(70\%\) for our identified deviation from the DRW model. It suggest that AGNs variability is a complex phenomenon and the DRW model is not suitable for the optical variability of all AGNs.


Quasar: general Variability: DRW model Methods: statistical 



We would like to thank Cai Zhenyi and Sun Mouyuan from University of Science and Technology of China and Hengxiao Guo from University of Illinois at Urbana-Champaig for their useful comments and discussion when preparing this paper. We also thank Kozłowski Szymon from Warsaw University Observatory give me useful discussion in the computational method. This work is supported by the National Key R\(\&\)D Program of China (No. 2018YFA0404502), the National Natural Science Foundation of China (NSFC grants 11733002 and 11773013), the Excellent Youth Foundation of the Jiangsu Scientific Committee (BK20150014), and National Key R\(\&\)D Program of China (No. 2017YFA0402704). H. Wang acknowledges support from the Science and Technology supporting Program in Langfang city (No.2018011005).


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.The School of Astronomy and Space ScienceNanjing UniversityNanjingChina
  2. 2.The Faculty of Physics and Electronic InformationLangfang Normal UniversityLangfangChina
  3. 3.Key Laboratory of Modern Astronomy and AstrophysicsNanjing UniversityNanjingChina

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