Estimating activity cycles with probabilistic methods I. Bayesian Generalised Lomb-Scargle Periodogram with Trend

Research output: Contribution to journalArticleScientificpeer-review

Researchers

Research units

  • Tartu Observatory
  • Max-Planck-Institut für Sonnensystemforschung

Abstract

Period estimation is one of the central topics in astronomical time series analysis, where data is often unevenly sampled. Especially challenging are studies of stellar magnetic cycles, as there the periods looked for are of the order of the same length than the datasets themselves. The datasets often contain trends, the origin of which is either a real long-term cycle or an instrumental effect, but these effects cannot be reliably separated, while they can lead to erroneous period determinations if not properly handled. In this study we aim at developing a method that can handle the trends properly, and by performing extensive set of testing, we show that this is the optimal procedure when contrasted with methods that do not include the trend directly to the model. The effect of the noise model on the results is also investigated. We introduce a Bayesian Generalised Lomb-Scargle Periodogram with Trend (BGLST), which is a probabilistic linear regression model using Gaussian priors for the coefficients and uniform prior for the frequency parameter. We show, using synthetic data, that when there is no prior information on whether and to what extent the true model of the data contains a linear trend, the introduced BGLST method is preferable to the methods which either detrend the data or leave the data untrended before fitting the periodic model. Whether to use different from constant noise model depends on the density of the data sampling as well as on the true noise model of the process.

Details

Original languageEnglish
Article numberA111
Pages (from-to)1-13
JournalAstronomy and Astrophysics
Volume615
Early online date2018
Publication statusPublished - Jul 2018
MoE publication typeA1 Journal article-refereed

    Research areas

  • Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Statistics - Applications, Statistics - Machine Learning

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