OGLE-2016-BLG-1266: A Probable Brown-Dwarf/Planet Binary at the Deuterium Fusion Limit

TL;DR

This paper reports the discovery of a low-mass binary system near the deuterium fusion limit, likely composed of brown dwarfs or super-Jupiter planets, using microlensing measurements from Earth and Spitzer.

Contribution

First measurement of a probable brown-dwarf/planet binary at the deuterium fusion boundary using combined Earth and space-based microlensing data.

Findings

Binary system with masses around 12 and 16 Jupiter masses.

Located at approximately 3.08 kpc in the Galactic Plane.

Projected separation of about 0.43 AU.

Abstract

We report the discovery, via the microlensing method, of a new very-low-mass binary system. By combining measurements from Earth and from the Spitzer telescope in Earth-trailing orbit, we are able to measure the microlensing parallax of the event, and find that the lens likely consists of an $(12.0 \pm 0.6) M_{\rm J}$ + $(15.7 \pm 1.5) M_{\rm J}$ super-Jupiter / brown-dwarf pair. The binary is located at a distance of $(3.08 \pm 0.18)$ kpc in the Galactic Plane, and the components have a projected separation of $(0.43 \pm 0.03)$ AU. Two alternative solutions with much lower likelihoods are also discussed, an 8- and 6-$M_{\rm J}$ model and a 90- and 70-$M_{\rm J}$ model. Although disfavored at the 3-$\sigma$ and 5-$\sigma$ levels, these alternatives cannot be rejected entirely. We show how the more-massive of these models could be tested with future direct imaging.