Systematic KMTNet Planetary Anomaly Search, Paper I: OGLE-2019-BLG-1053Lb, A Buried Terrestrial Planet

Abstract

In order to exhume the buried signatures of "missing planetary caustics" in the KMTNet data, we conducted a systematic anomaly search to the residuals from point-source point-lens fits, based on a modified version of the KMTNet EventFinder algorithm. This search reveals the lowest mass-ratio planetary caustic to date in the microlensing event OGLE-2019-BLG-1053, for which the planetary signal had not been noticed before. The planetary system has a planet-host mass ratio of $q=(1.25\pm 0.13)\times 10^{-5}$. A Bayesian analysis yields estimates of the mass of the host star, $M_{\mathrm{host}}=0.61_{-0.24}^{+0.29}{M}_{\odot }$, the mass of its planet, $M_{\mathrm{planet}}=2.48_{-0.98}^{+1.19}{M}_{\oplus }$, the projected planet-host separation, $a_{\perp }=3.4_{-0.5}^{+0.5}$ au, and the lens distance of $D_{\mathrm{L}}=6.8_{-0.9}^{+0.6}$ kpc. The discovery of this very low mass-ratio planet illustrates the utility of our method and opens a new window for a large and homogeneous sample to study the microlensing planet-host mass-ratio function down to $q\sim 10^{-5}$.

published by AJ