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

Abstract

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^(+3.5)_(−1.8) M_(jup) and 0.090^(+0.096)_(−0.037) 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.

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