Gravitational Binary-lens Events with Prominent Effects of Lens Orbital Motion

TL;DR

This paper analyzes binary-lens microlensing events, emphasizing the importance of including lens orbital motion in models to accurately determine physical parameters, as orbital effects significantly influence light curve deviations.

Contribution

It demonstrates that considering lens orbital motion is crucial for accurate modeling of binary-lens microlensing events, correcting potential biases from neglecting these effects.

Findings

Orbital motion explains most deviations in analyzed light curves.

Neglecting orbital effects can lead to incorrect lens parameter estimates.

Lens OGLE-2006-BLG-277 is a low-mass star with a brown dwarf companion.

Abstract

Gravitational microlensing events produced by lenses composed of binary masses are important because they provide a major channel to determine physical parameters of lenses. In this work, we analyze the light curves of two binary-lens events OGLE-2006-BLG-277 and OGLE-2012-BLG-0031 for which the light curves exhibit strong deviations from standard models. From modeling considering various second-order effects, we find that the deviations are mostly explained by the effect of the lens orbital motion. We also find that lens parallax effects can mimic orbital effects to some extent. This implies that modeling light curves of binary-lens events not considering orbital effects can result in lens parallaxes that are substantially different from actual values and thus wrong determinations of physical lens parameters. This demonstrates the importance of routine consideration of orbital effects in interpreting light curves of binary-lens events. It is found that the lens of OGLE-2006-BLG-277 is a binary composed of a low-mass star and a brown dwarf companion.