The Importance of Binary Gravitational Microlensing Events Through High-Magnification Channel

TL;DR

This paper evaluates the high detection efficiency of binary gravitational microlensing events in high-magnification scenarios, highlighting their significance for planetary detection and statistical studies of binary systems.

Contribution

It provides a simple method to estimate detection efficiency, demonstrating high sensitivity across wide parameter ranges, and emphasizes the importance of high-magnification events in microlensing surveys.

Findings

Detection efficiency approaches 100% for certain separation ranges at high magnifications.

High efficiency covers nearly the entire mass-ratio range of stellar companions.

Most binary-lens events can be detected through high-magnification channels.

Abstract

We estimate the detection efficiency of binary gravitational lensing events through the channel of high-magnification events. From this estimation, we find that binaries in the separations ranges of 0.1 < s < 10, 0.2 < s < 5, and 0.3 < s < 3 can be detected with ~ 100% efficiency for events with magnifications higher than A=100, 50, and 10, respectively, where s represents the projected separation between the lens components normalized by the Einstein radius. We also find that the range of high efficiency covers nearly the whole mass-ratio range of stellar companions. Due to the high efficiency in wide ranges of parameter space, we point out that majority of binary-lens events will be detected through the high-magnification channel in lensing surveys that focus on high-magnification events for efficient detections of microlensing planets. In addition to the high efficiency, the simplicity of the efficiency estimation makes the sample of these binaries useful in the statistical studies of the distributions of binary companions as functions of mass ratio and separation. We also discuss other importance of these events.