Spitzer Observations of OGLE-2015-BLG-1212 Reveal a New Path to Breaking Strong Microlens Degeneracies

TL;DR

This paper demonstrates how Spitzer space telescope observations can resolve microlensing degeneracies, specifically distinguishing between planetary and binary lens models, leading to clearer identification of stellar binaries in the Galactic bulge.

Contribution

The study introduces a method using space-based parallax observations to effectively break degeneracies in microlensing models, improving the accuracy of lens system characterization.

Findings

Only 8 out of 32 models remain after analysis.

The lens is identified as a stellar binary, likely in the Galactic bulge.

Space-based parallax observations can resolve various microlensing degeneracies.

Abstract

Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively breaks a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered. Only eight viable models survive out of an initial set of 32 local minima in the parameter space. These models clearly indicate that the lens is a stellar binary system possibly located within the bulge of our Galaxy, ruling out the planetary alternative. We argue that several types of discrete degeneracies can be broken via such space-based parallax observations.