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

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 we find that the lens likely consists of a (12.0 0.6)MJ + (15.7 1.5)MJ super-Jupiter/brown dwarf pair. The binary is located at a distance of 3.08 0.18 kpc in the Galactic plane, and the components have a projected separation of 0.43 0.03 au. Two alternative solutions with much lower likelihoods are also discussed, an 8MJ and 6MJ model and a 90MJ and 70MJ model. If all photometric measurements were independent and Gaussian distributed with known variances, these alternative solutions would be formally disfavored at the 3 and 5 levels. We show how the more massive of these models could be tested with future direct imaging.