Space-based Microlens Parallax Observation As a Way to Resolve the Severe Degeneracy between Microlens-parallax and Lens-orbital Effect

TL;DR

This paper demonstrates how space-based microlens parallax observations can resolve the severe degeneracy between microlens-parallax and lens-orbital effects, improving the accuracy of binary lens parameter determination.

Contribution

It shows that space-based observations can effectively distinguish between higher-order effects, enhancing the analysis of gravitational microlensing events.

Findings

Degeneracy between microlens-parallax and lens-orbital effects is severe.

Space-based data can resolve this degeneracy.

Improved parameter estimation for binary lenses.

Abstract

In this paper, we demonstrate the severity of the degeneracy between the microlens-parallax and lens-orbital effects by presenting the analysis of the gravitational binary-lens event OGLE-2015-BLG-0768. Despite the obvious deviation from the model based on the the linear observer motion and the static binary, it is found that the residual can be almost equally well explained by either the parallactic motion of the Earth or the rotation of the binary lens axis, resulting in the severe degeneracy between the two effects. We show that the degeneracy can be readily resolved with the additional data provided by space-based microlens parallax observations. Enabling to distinguish between the two higher-order effects, space-based microlens parallax observations will make it possible not only to accurately determine the physical lens parameters but also to further constrain the orbital parameters of binary lenses.