Abstract

Celestial objects exhibit a wide range of variability in brightness at different wavebands. Surprisingly, the most common methods for characterizing time series in statistics -- parametric autoregressive modeling -- is rarely used to interpret astronomical light curves. We review standard ARMA, ARIMA and ARFIMA (autoregressive moving average fractionally integrated) models that treat short-memory autocorrelation, long-memory $1/f^\alpha$ `red noise', and nonstationary trends. Though designed for evenly spaced time series, moderately irregular cadences can be treated as evenly-spaced time series with missing data. Fitting algorithms are efficient and software implementations are widely available. We apply ARIMA models to light curves of four variable stars, discussing their effectiveness for different temporal characteristics. A variety of extensions to ARIMA are outlined, with emphasis on recently developed continuous-time models like CARMA and CARFIMA designed for irregularly spaced time series. Strengths and weakness of ARIMA-type modeling for astronomical data analysis and astrophysical insights are reviewed.

Highlights

  • Frontiers in PhysicsCelestial objects exhibit a wide range of variability in brightness at different wavebands

  • We review standard ARMA, ARIMA, and ARFIMA models that treat short-memory autocorrelation, long-memory 1/fα “red noise,” and nonstationary trends

  • A variety of extensions to ARIMA are outlined, with emphasis on recently developed continuous-time models like CARMA and CARFIMA designed for irregularly spaced time series

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Summary

Frontiers in Physics

Celestial objects exhibit a wide range of variability in brightness at different wavebands. The most common methods for characterizing time series in statistics—parametric autoregressive modeling—are rarely used to interpret astronomical light curves. We review standard ARMA, ARIMA, and ARFIMA (autoregressive moving average fractionally integrated) models that treat short-memory autocorrelation, long-memory 1/fα “red noise,” and nonstationary trends. Though designed for evenly spaced time series, moderately irregular cadences can be treated as evenly-spaced time series with missing data. We apply ARIMA models to light curves of four variable stars, discussing their effectiveness for different temporal characteristics. A variety of extensions to ARIMA are outlined, with emphasis on recently developed continuous-time models like CARMA and CARFIMA designed for irregularly spaced time series. Strengths and weakness of ARIMA-type modeling for astronomical data analysis and astrophysical insights are reviewed

THE VARIABILITY OF COSMIC POPULATIONS
TESTING THE MODEL
SOFTWARE IMPLEMENTATIONS IN R
APPLICATION TO STELLAR PHOTOMETRY
EXTENSIONS TO ARIMA
Exogeneous Covariates
Regime Switching
State Space Modeling
CONTINUOUS TIME MODELING FOR IRREGULAR ASTRONOMICAL TIME SERIES
INSIGHTS FROM AUTOREGRESSIVE MODELING
Identifying Change Points
Classifying Time Series
Understanding Astrophysical Processes
Findings
CONCLUDING COMMENTS

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