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, $q<2\times 10^{-4}$. 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.

Figures (21)

• Figure 1: Mass-Measurements of 24 microlensing hosts for events occurring 2005-2014. The magenta numbers show the total number of planetary events for each year. The colors give the method of mass measurement, as indicated just above the image. Specifically: (1) Late-time high-resolution imaging ob05169batob05169bengould22 ("IMAGE", red, 11); (2) Combining light-curve measurements of the microlens parallax ($\pi_{\rm E}$) and Einstein radius ($\theta_{\rm E}$) to yield $M=\theta_{\rm E}/\kappa\pi_{\rm E}$gould92 ("PAR", green, 9); (3) Combining light curve measurements of $\pi_{\rm E}$ with excess light, relative to the source flux derived from the light curve ob06109b, ("PAR+EXC-LIGHT", cyan, 2); (4) Mass derived from excess-light alone mb11293b ("EXC-LIGHT", blue, 2).
• Figure 2: Color-magnitude diagrams (CMDs) for the five events analyzed in this paper. The positions of the source (blue), clump-giant centroid (red), and blend (green) are marked.
• Figure 3: Light curve and models for KMT-2023-BLG-0164. For the four caustic-geometry insets at the right, the light-colored caustics represent the configurations at $t=t_0$, while the dark-colored caustics represent $t=t_{\rm anom}$.
• Figure 4: Parallax contours for the four solutions of KMT-2023-BLG-0164. Colors indicate values of $\Delta\chi^2<1,4,9,16,25,36$.
• Figure 5: Scatter plots of the normalized source radius, $\rho$, against the values of $\Delta\chi^2$ relative to the best fit for each of the four solutions of KMT-2023-BLG-0164. Colors indicate values of $\Delta\chi^2<1,4,9,16,25,36$. Also shown is the adopted envelope function, which is used in Section \ref{['sec:phys']}.