Time series analysis in astronomy - an application to quasar variability studies

Abstract

The topic of luminosity variations of astronomical objects is considered, and the general problem of analyzing temporal data in astronomy is discussed. This topic is examined in the context of quasar variability in order to test the performances of the various statistical methods in a given experimental ambit. It is shown that in the study of astronomical time series, the power-spectrum (even in the maximum entropy or CLEAN version) and the structure-function techniques are often of little use or even misleading, since they do not take into account all the information contained in the data. The effects of the discrete sampling of the signal are also considered, and the evolution of a single system and that of a multiple subunit system are distinguished. The approach based on phase-space reconstruction algorithms and on dimension and entropy estimators as derived from the theory of nonlinear dynamical systems is discussed as well.