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

TL;DR

This paper reports the systematic search for low mass-ratio planets in 2023 KMTNet microlensing data, identifying three strong candidates and analyzing their properties, with implications for understanding planet populations.

Contribution

First systematic search using re-reduced 2023 KMTNet data focusing on low mass-ratio planets, discovering three strong candidates and detailed characterization of one host star.

Findings

Identified three strong low-$q$ planet candidates.

Characterized the host star of KMT-2023-BLG-0164 as a 1.0 solar mass star at 1.5 kpc.

Re-reduction of photometry increased sensitivity to low-mass planets.

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, $q<2\times 10^{-4}$. 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 ($q\sim 1.3\times 10^{-4}$), KMT-2023-BLG-1286 ($q\sim 1.9\times 10^{-4}$), and KMT-2023-BLG-1746 ($q\sim 8\times 10^{-5}$). 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 $M\sim 1.0\,M_\odot$ and $D\sim 1.5$ kpc, 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 due to their ambiguous interpretations as possible non-planetary events.