Journal Article

KeplerPresearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction

Girouard, Forrest R., Twicken, Joseph D., Smith, Jeffrey C., Kolodziejczak, Jeffery J., Fanelli, Michael N., Jenkins, Jon M., McCauliff, Sean D., Morris, Robert L., Barclay, Thomas S., Stumpe, Martin C., Van Cleve, Jeffrey E.

2012

Overview

With the unprecedented photometric precision of theKeplerspacecraft, significant systematic and stochastic errors on transit signal levels are observable in theKeplerphotometric data. These errors, which include discontinuities, outliers, systematic trends, and other instrumental signatures, obscure astrophysical signals. The presearch data conditioning (PDC) module of theKeplerdata analysis pipeline tries to remove these errors while preserving planet transits and other astrophysically interesting signals. The completely new noise and stellar variability regime observed inKeplerdata poses a significant problem to standard cotrending methods. Variable stars are often of particular astrophysical interest, so the preservation of their signals is of significant importance to the astrophysical community. We present a Bayesian maximum a posteriori (MAP) approach, where a subset of highly correlated and quiet stars is used to generate a cotrending basis vector set, which is in turn used to establish a range of “reasonable” robust fit parameters. These robust fit parameters are then used to generate a Bayesian prior and a Bayesian posterior probability distribution function (PDF) which, when maximized, finds the best fit that simultaneously removes systematic effects while reducing the signal distortion and noise injection that commonly afflicts simple least-squares (LS) fitting. A numerical and empirical approach is taken where the Bayesian prior PDFs are generated from fits to the light-curve distributions themselves.

• Publisher: University of Chicago Press