Random Forests applied to High Precision Photometry Analysis with Spitzer IRAC

TL;DR

This paper introduces a machine learning approach using Random Forests to correct systematic errors in high-precision photometry from Spitzer IRAC, enabling accurate measurement of exoplanet eclipse depths.

Contribution

The study develops a novel Random Forest-based correction method that leverages calibration data, improving the accuracy and speed of analyzing IRAC photometry for exoplanet studies.

Findings

Random Forests effectively reduce systematic errors in IRAC photometry.

Measured eclipse depth of XO-3b consistent with literature, with larger uncertainty.

Caution advised in model validation to avoid overestimating correction accuracy.

Abstract

We present a new method employing machine learning techniques for measuring astrophysical features by correcting systematics in IRAC high precision photometry using Random Forests. The main systematic in IRAC light curve data is position changes due to unavoidable telescope motions coupled with an intrapixel response function. We aim to use the large amount of publicly available calibration data for the single pixel used for this type of work (the sweet spot pixel) to make a fast, easy to use, accurate correction to science data. This correction on calibration data has the advantage of using an independent dataset instead of using the science data on itself, which has the disadvantage of including astrophysical variations. After focusing on feature engineering and hyperparameter optimization, we show that a boosted random forest model can reduce the data such that we measure the median of ten archival eclipse observations of XO-3b to be 1459 +- 200 parts per million. This is a comparable depth to the average of those in the literature done by seven different methods, however the spread in measurements is 30-100% larger than those literature values, depending on the reduction method. We also caution others attempting similar methods to check their results with the fiducial dataset of XO-3b as we were also able to find models providing initially great scores on their internal test datasets but whose results significantly underestimated the eclipse depth of that planet.