OGLE-2008-BLG-510: first automated real-time detection of a weak microlensing anomaly - brown dwarf or stellar binary?

TL;DR

This paper reports the first automated real-time detection of a weak microlensing anomaly, demonstrating the feasibility and challenges of identifying subtle features in microlensing light curves for statistical and astrophysical insights.

Contribution

It introduces a method for automated real-time detection of weak microlensing anomalies and discusses the importance of comprehensive modeling and high data quality.

Findings

Automated detection of weak anomalies is feasible and efficient.

Weak features often have ambiguities that require thorough modeling.

High data quality is essential to distinguish real features from systematics.

Abstract

The microlensing event OGLE-2008-BLG-510 is characterised by an evident asymmetric shape of the peak, promptly detected by the ARTEMiS system in real time. The skewness of the light curve appears to be compatible both with binary-lens and binary-source models, including the possibility that the lens system consists of an M dwarf orbited by a brown dwarf. The detection of this microlensing anomaly and our analysis demonstrates that: 1) automated real-time detection of weak microlensing anomalies with immediate feedback is feasible, efficient, and sensitive, 2) rather common weak features intrinsically come with ambiguities that are not easily resolved from photometric light curves, 3) a modelling approach that finds all features of parameter space rather than just the `favourite model' is required, and 4) the data quality is most crucial, where systematics can be confused with real features, in particular small higher-order effects such as orbital motion signatures. It moreover becomes apparent that events with weak signatures are a silver mine for statistical studies, although not easy to exploit. Clues about the apparent paucity of both brown-dwarf companions and binary-source microlensing events might hide here.