基于集合经验模态分解的类星体光变周期及其混沌特性分析

Variability periodicity and chaotic property of quasars based on ensemble empirical mode decomposition

基于密歇根大学射电天文台数据库中从1965年到2012年收集的类星体3C 345,3C 273和3C 279在射电8.0 GHz的光变数据,利用集合经验模态分解方法将这些类星体的光变资料分解为周期项、趋势项和高频项,并对分解后的高频项计算其饱和关联维数、最大Lyapunov指数和Kolmogorov熵,判断是否具有混沌性.结果表明,这些类星体的光变不仅具有周期性,也具有明显的混沌特性,表明类星体光变应为产生周期性运动的物理机制和产生混沌现象的非线性机制的综合结果.

The radio fluxes of the quasars 3C 345, 3C 279 and 3C 273 at a frequency of 8.0 GHz were collected in a time period from 1965 to 2012 based on the database of University of Michigan Radio Astronomy Observatory. The time series of the quasar variability is decomposed into trend components, periodic components and high frequency components by the ensemble empirical mode decomposition. Then chaotic characteristic quantities of the high frequency component is analyzed, that is, saturation correlation dimension, maximum Lyapunov exponent and Kolmogorov entropy. The results show that the variability of quasars has the chaotic characteristic as well as the characteristic of periodicity. The variability of quasars is due to the comprehensive consequence of a physical mechanism of the periodic phenomenon combined with the nonlinear mechanism of the chaos phenomenon.