# OGLE-2016-BLG-1003: First Resolved Caustic-crossing Binary-source Event Discovered by Second-generation Microlensing Surveys

## TL;DR

This paper presents the first resolved caustic-crossing binary-source microlensing event, demonstrating the importance of high-cadence observations and second-generation surveys in detecting complex lensing phenomena.

## Contribution

It reports the discovery and analysis of a unique binary-source microlensing event with nested caustic crossings, highlighting observational and analytical advancements.

## Key findings

- First resolved caustic-crossing binary-source event
- High-cadence, continuous observations are crucial
- Complex perturbations can be identified by second-generation surveys

## Abstract

We report the analysis of the first resolved caustic-crossing binary-source microlensing event OGLE-2016-BLG-1003. The event is densely covered by the round-the-clock observations of three surveys. The light curve is characterized by two nested caustic-crossing features, which is unusual for typical caustic-crossing perturbations. From the modeling of the light curve, we find that the anomaly is produced by a binary source passing over a caustic formed by a binary lens. The result proves the importance of high-cadence and continuous observations, and the capability of second-generation microlensing experiments to identify such complex perturbations that are previously unknown. However, the result also raises the issues of the limitations of current analysis techniques for understanding lens systems beyond two masses and of determining the appropriate multiband observing strategy of survey experiments.