Abstract
Abstract We analyze the combined Spitzer and ground-based data for OGLE-2017-BLG-1140 and show that the event was generated by a Jupiter-class planet orbiting a mid-late M dwarf that lies in the foreground of the microlensed Galactic-bar source star. The planet–host projected separation is , i.e., well beyond the snow line. By measuring the source proper motion from ongoing long-term OGLE imaging and combining this with the lens-source relative proper motion derived from the microlensing solution, we show that the lens proper motion is consistent with the lens lying in the Galactic disk, although a bulge lens is not ruled out. We show that while the Spitzer and ground-based data are comparably well fitted by planetary (i.e., binary-lens (2L1S)) and binary-source (1L2S) models, the combination of Spitzer and ground-based data decisively favors the planetary model. This is a new channel to resolve the 2L1S/1L2S degeneracy, which can be difficult to break in some cases.
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