Red noise versus planetary interpretations in the microlensing event OGLE-2013-BLG-446

TL;DR

This paper examines the microlensing event OGLE-2013-BLG-446 to assess whether observed signals indicating a low-mass planetary companion are genuine or caused by systematic errors, emphasizing the importance of error analysis.

Contribution

The study introduces a method to evaluate systematic errors in microlensing data, demonstrating its application on a real event to distinguish true planetary signals from artifacts.

Findings

Systematic errors can mimic planetary signals in microlensing data.

The data do not support a planetary interpretation when systematics are considered.

Real-time modeling suggested a low-mass companion, but this was not confirmed after error analysis.

Abstract

For all exoplanet candidates, the reliability of a claimed detection needs to be assessed through a careful study of systematic errors in the data to minimize the false positives rate. We present a method to investigate such systematics in microlensing datasets using the microlensing event OGLE-2013-BLG-0446 as a case study. The event was observed from multiple sites around the world and its high magnification (A_{max} \sim 3000) allowed us to investigate the effects of terrestrial and annual parallax. Real-time modeling of the event while it was still ongoing suggested the presence of an extremely low-mass companion (\sim 3M_\oplus ) to the lensing star, leading to substantial follow-up coverage of the light curve. We test and compare different models for the light curve and conclude that the data do not favour the planetary interpretation when systematic errors are taken into account.