A Blind Method to Detrend Instrumental Systematics in Exoplanetary Light-curves

A blind method to detrend instrumental systematics in exoplanetary light-curves

Author:

Morello

Abstract:

The study of the atmospheres of exoplanets requires a photometric precision, and repeatability, at the level of one part in ~10^4. This is beyond the original calibration plans of current observatories, hence the necessity to disentangle some of the instrumental systematics from the astrophysical signals in raw datasets. Most methods used in the literature are parametric, i.e. based on an approximate model of the instrument, and therefore they have many degrees of freedom, which are, most likely, the cause of several controversies in the literature. Non-parametric methods have been proposed to guarantee an higher degree of objectivity (Carter & Winn 2009; Thatte et al. 2010; Gibson et al. 2012; Waldmann 2012; Waldmann et al. 2013; Waldmann 2014). Recently, Morello et al. (2014, 2015) have developed a non-parametric detrending method that gave coherent and repeatable results when applied to Spitzer/IRAC datasets that were debated in the literature. Said method is based on Independent Component Analysis (ICA) applied to individual pixel time-series, hereafter "pixel-ICA". The main purpose of this paper is to investigate the limits and advantages of pixel-ICA on a series of simulated datasets. We focus in particular on two mechanisms that cause systematics similar to the Spitzer/IRAC ones, then we generate several datasets to analyze, with different time scales, non-stationarity, sudden change points, etc. The performances of pixel-ICA detrending method are compared against the ones of a traditional polynomial centroid division (PCD) method.