KMT-2016-BLG-1107: A New Hollywood-planet Close/Wide Degeneracy

We show that microlensing event KMT-2016-BLG-1107 displays a new type of degeneracy between wide-binary and close-binary Hollywood events in which a giant-star source envelops the planetary caustic. The planetary anomaly takes the form of a smooth, two-day “bump” far out on the falling wing of the light curve, which can be interpreted either as the source completely enveloping a minor-image caustic due to a close companion with mass ratio q = 0.036, or partially enveloping a major-image caustic due to a wide companion with q = 0.004. The best estimates of the companion masses are both in the planetary regime ({3.3}_-1.8^+3.5 {M}_jup} and {0.090}_-0.037^+0.096 {M}_jup}) but differ by an even larger factor than the mass ratios due to different inferred host masses. We show that the two solutions can be distinguished by high-resolution imaging at first light on next-generation (“30 m”) telescopes. We provide analytic guidance to understand the conditions under which this new type of degeneracy can appear.