Interpretation of Strong Short-Term Central Perturbations in the Light Curves of Moderate-Magnification Microlensing Events

TL;DR

This paper analyzes short-term perturbations in microlensing light curves to distinguish between binary star systems and planetary signals, improving planet detection accuracy in high-magnification events.

Contribution

It identifies characteristic features of binary-lens events that help differentiate them from planetary signals in microlensing light curves.

Findings

Short-term perturbations near light curve peaks are caused by binary companions.

Binary-lens events exhibit specific caustic-crossing features.

These features can be used to discriminate between binary and planetary signals.

Abstract

To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that central perturbations can also be produced by binary companions and thus it is important to distinguish planetary signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007-BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short time-scale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.