Mass Production of 2023 KMTNet Microlensing Planets. I. Low Mass Ratio

Abstract We initiate the systematic search for planets in the 2023 data of the Korea Microlensing Telescope Network (KMTNet), focusing on those planets found by the KMTNet AnomalyFinder with low preliminary estimates of the mass ratio, q < 2 × 10 −4 . The 2023 season is the first for which the photometry of all events was re-reduced prior to the AnomalyFinder search, potentially increasing its sensitivity to planets. We find three strong low- q planet candidates, KMT-2023-BLG-0164 ( q ∼ 1.3 × 10 −4 ), KMT-2023-BLG-1286 ( q ∼ 1.9 × 10 −4 ), and KMT-2023-BLG-1746 ( q ∼ 8 × 10 −5 ). KMT-2023-BLG-0164 is notable in that the source is projected on a very bright ( I = 16.0) foreground star, which is either the planet’s host or (more likely) a companion to the host. We obtain a spectrum, finding that its mass and distance are M ∼ 1.0 M ⊙ and D ∼ 1.5 kpc, respectively, the latter being the distance of the lens ( D L ) regardless of whether the spectroscopic target is the host or its companion. We also analyze two other candidates, KMT-2023-BLG-0614 and KMT-2023-BLG-1593, which are unlikely to enter the statistical sample owing to their ambiguous interpretations as possible nonplanetary events.