Wavelets in Unevenly Spaced Data: OJ 287 light curve

Abstract

The three factors that often characterize astronomical time series are uneven spacing, noise and the small number of data points Because of these limiting factors data analysis methods should themselves be studied before applying them to the data. We have investigated scale-grams using Haar wavelets in simulated data sets with various samplings. We point out sampling artifacts and introduce a revised scalegram which we call noisegram. We also apply this method to the century long optical V-band flux density light curve of the blazar OJ 287 to analyze its variations on time scales from a day to a century and indicate the presence of variability over the entire range.